Add reliable tag on plan qa tests

This is the first iteration to address the first two checkboxes of
https://gitlab.com/gitlab-org/quality/team-tasks/issues/337

Another MR will be created for the new pipeline job that will run
the reliable tests.

qa/qa/specs/features/browser_ui/2_plan/email/trigger_email_notification_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan', :orchestrated, :smtp do
+  context 'Plan', :orchestrated, :smtp, :reliable do
     describe 'Email Notification' do
       let(:user) do
         Resource::User.fabricate_or_use(Runtime::Env.gitlab_qa_username_1, Runtime::Env.gitlab_qa_password_1)

qa/qa/specs/features/browser_ui/2_plan/issue/check_mentions_for_xss_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'check xss occurence in @mentions in issues', :requires_admin do
       it 'user mentions a user in comment' do
         QA::Runtime::Env.personal_access_token = QA::Runtime::Env.admin_personal_access_token

qa/qa/specs/features/browser_ui/2_plan/issue/close_issue_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Close issue' do
       let(:issue) do
         Resource::Issue.fabricate_via_api!

qa/qa/specs/features/browser_ui/2_plan/issue/collapse_comments_in_discussions_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'collapse comments in issue discussions' do
       let(:my_first_reply) { 'My first reply' }
 

qa/qa/specs/features/browser_ui/2_plan/issue/comment_issue_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Issue comments' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/browser_ui/2_plan/issue/create_issue_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan', :smoke do
+  context 'Plan', :smoke, :reliable do
     describe 'Issue creation' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/browser_ui/2_plan/issue/filter_issue_comments_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'filter issue comments activities' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/browser_ui/2_plan/issue/issue_suggestions_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'issue suggestions' do
       let(:issue_title) { 'Issue Lists are awesome' }
 

qa/qa/specs/features/browser_ui/2_plan/issue/mentions_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan', :smoke do
+  context 'Plan', :smoke, :reliable do
     describe 'mention' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/api/2_plan/epics_milestone_dates_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Epics milestone dates API' do
       before(:context) do
         @api_client = Runtime::API::Client.new(:gitlab)

qa/qa/specs/features/ee/browser_ui/2_plan/burndown_chart/burndown_chart_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Burndown chart' do
       include ::QA::Support::Dates
 

qa/qa/specs/features/ee/browser_ui/2_plan/custom_email/custom_email_spec.rb

@@ -3,7 +3,7 @@
 require 'securerandom'
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Custom email', :requires_admin do
       before do
         Flow::Login.sign_in_as_admin

qa/qa/specs/features/ee/browser_ui/2_plan/epic/epics_management_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Epics Management' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/epic/promote_issue_to_epic_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'promote issue to epic' do
       it 'user promotes issue to an epic' do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/epic/roadmap_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Epics roadmap' do
       include Support::Dates
 

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/configurable_issue_board_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Configurable issue board' do
       let(:label_board_list) do
         EE::Resource::Board::BoardList::Project::LabelBoardList.fabricate_via_api!

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/configure_issue_board_by_label_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Configure issue board by label' do
       let(:label_board_list) do
         EE::Resource::Board::BoardList::Project::LabelBoardList.fabricate_via_api!

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/create_group_issue_board_spec.rb

@@ -3,7 +3,7 @@
 require 'securerandom'
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Group issue boards' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/focus_mode_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Issue board focus mode' do
       let(:project) do
         QA::Resource::Project.fabricate_via_api! do |project|

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/group_issue_boards_spec.rb

@@ -3,7 +3,7 @@
 require 'securerandom'
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Group issue boards' do
       let(:board_1) { "Board-#{SecureRandom.hex(4)}" }
       let(:board_2) { "Board-#{SecureRandom.hex(4)}" }

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/project_issue_boards_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Project issue boards' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/read_only_board_configuration_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Read-only board configuration' do
       let(:qa_user) do
         Resource::User.fabricate_or_use(Runtime::Env.gitlab_qa_username_1, Runtime::Env.gitlab_qa_password_1)

qa/qa/specs/features/ee/browser_ui/2_plan/issue_boards/sum_of_issues_weights_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Sum of issues weights on issue board' do
       let(:label_board_list) do
         EE::Resource::Board::BoardList::Project::LabelBoardList.fabricate_via_api!

qa/qa/specs/features/ee/browser_ui/2_plan/issues_analytics/issues_analytics_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Issues analytics' do
       let(:issue) do
         Resource::Issue.fabricate_via_api!

qa/qa/specs/features/ee/browser_ui/2_plan/issues_list/export_as_csv_spec.rb

@@ -3,7 +3,7 @@
 require 'securerandom'
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Issues list' do
       let(:project) do
         Resource::Project.fabricate_via_api! do |project|

qa/qa/specs/features/ee/browser_ui/2_plan/issues_weight/issue_weight_visualization_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Issues weight visualization' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/multiple_assignees_for_issues/four_assignees_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Multiple assignees per issue' do
       before do
         Flow::Login.sign_in

qa/qa/specs/features/ee/browser_ui/2_plan/multiple_assignees_for_issues/more_than_four_assignees_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Multiple assignees per issue' do
       let(:project) do
         Resource::Project.fabricate_via_api! do |resource|

qa/qa/specs/features/ee/browser_ui/2_plan/related_issues/related_issues_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Related issues' do
       let(:project) do
         Resource::Project.fabricate_via_api! do |project|

qa/qa/specs/features/ee/browser_ui/2_plan/scoped_labels/editing_scoped_labels_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Plan' do
+  context 'Plan', :reliable do
     describe 'Editing scoped labels on issues' do
       let(:initial_label) { 'animal::fox' }
       let(:new_label_same_scope) { 'animal::dolphin' }