Fix Rails/SaveBang offenses in ee/spec/controllers

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/220040.

.rubocop_manual_todo.yml

@@ -29,8 +29,6 @@ Graphql/Descriptions:
 # WIP: See https://gitlab.com/gitlab-org/gitlab/-/issues/220040
 Rails/SaveBang:
   Exclude:
-    - 'ee/spec/controllers/projects/merge_requests_controller_spec.rb'
-    - 'ee/spec/controllers/subscriptions_controller_spec.rb'
     - 'ee/spec/initializers/fog_google_https_private_urls_spec.rb'
     - 'ee/spec/lib/analytics/merge_request_metrics_calculator_spec.rb'
     - 'ee/spec/lib/ee/gitlab/auth/ldap/sync/group_spec.rb'

ee/spec/controllers/projects/merge_requests_controller_spec.rb

@@ -68,7 +68,7 @@ RSpec.describe Projects::MergeRequestsController do
     end
 
     before do
-      project.update(approvals_before_merge: 2)
+      project.update!(approvals_before_merge: 2)
     end
 
     def update_merge_request(params = {})
@@ -173,7 +173,7 @@ RSpec.describe Projects::MergeRequestsController do
 
     shared_examples 'approvals_before_merge param' do
       before do
-        project.update(approvals_before_merge: 2)
+        project.update!(approvals_before_merge: 2)
       end
 
       context 'approvals_before_merge not set for the existing MR' do
@@ -314,7 +314,7 @@ RSpec.describe Projects::MergeRequestsController do
 
         before do
           project.add_developer(user)
-          project.update(approvals_before_merge: 0)
+          project.update!(approvals_before_merge: 0)
         end
 
         it_behaves_like 'approvals_before_merge param'

ee/spec/controllers/subscriptions_controller_spec.rb

@@ -237,7 +237,7 @@ RSpec.describe SubscriptionsController do
         let(:group) { Group.new(path: 'foo') }
 
         it 'returns the errors in json format' do
-          group.save
+          group.save!
           subject
 
           expect(response.body).to include({ name: ["can't be blank"] }.to_json)
@@ -247,7 +247,7 @@ RSpec.describe SubscriptionsController do
           let(:group) { Group.new(path: 'foo', name: '<script>alert("attack")</script>') }
 
           it 'returns the errors in json format' do
-            group.save
+            group.save!
             subject
 
             expect(Gitlab::Json.parse(response.body)['name']).to match_array([Gitlab::Regex.group_name_regex_message, HtmlSafetyValidator.error_message])