Cleanup sticky_environments_in_job_retry feature flag

This commit cleans up the feature flag as it's
deemed stable.

Changelog: fixed

app/services/ci/retry_build_service.rb

@@ -77,13 +77,8 @@ module Ci
     end
 
     def deployment_attributes_for(new_build, old_build)
-      if Feature.enabled?(:sticky_environments_in_job_retry, project, default_enabled: :yaml)
-        ::Gitlab::Ci::Pipeline::Seed::Build
-          .deployment_attributes_for(new_build, old_build.persisted_environment)
-      else
-        ::Gitlab::Ci::Pipeline::Seed::Build
-          .deployment_attributes_for(new_build)
-      end
+      ::Gitlab::Ci::Pipeline::Seed::Build
+        .deployment_attributes_for(new_build, old_build.persisted_environment)
     end
   end
 end

config/feature_flags/development/sticky_environments_in_job_retry.yml

----
-name: sticky_environments_in_job_retry
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/72970
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/343874
-milestone: '14.5'
-type: development
-group: group::release
-default_enabled: false

spec/services/ci/retry_build_service_spec.rb

@@ -354,22 +354,6 @@ RSpec.describe Ci::RetryBuildService do
         it 'does not create a new environment' do
           expect { new_build }.not_to change { Environment.count }
         end
-
-        context 'when sticky_environments_in_job_retry feature flag is disabled' do
-          before do
-            stub_feature_flags(sticky_environments_in_job_retry: false)
-          end
-
-          it 'creates a new environment' do
-            expect { new_build }.to change { Environment.count }
-          end
-
-          it 'ignores the previous persisted environment' do
-            expect(build.persisted_environment.name).to eq("review/#{build.ref}-#{other_developer.id}")
-
-            expect(new_build.persisted_environment.name).to eq("review/#{build.ref}-#{developer.id}")
-          end
-        end
       end
 
       context 'when build has needs' do