Remove the code_review_async_pipeline_creation feature flag

MR: gitlab.com/gitlab-org/gitlab/-/merge_requests/59624
Issue: gitlab.com/gitlab-org/gitlab/-/issues/327559

app/services/merge_requests/refresh_service.rb

@@ -162,12 +162,7 @@ module MergeRequests
     end
 
     def refresh_pipelines_on_merge_requests(merge_request)
-      if Feature.enabled?(:code_review_async_pipeline_creation, project, default_enabled: :yaml)
-        create_pipeline_for(merge_request, current_user, async: true)
-      else
-        create_pipeline_for(merge_request, current_user, async: false)
-        UpdateHeadPipelineForMergeRequestWorker.perform_async(merge_request.id)
-      end
+      create_pipeline_for(merge_request, current_user, async: true)
     end
 
     def abort_auto_merges(merge_request)

changelogs/unreleased/327559-feature-flag-rollout-of-code_review_async_pipeline_creation.yml

+---
+title: Create the merge request pipeline asynchronously on push
+merge_request: 59624
+author:
+type: performance

config/feature_flags/development/code_review_async_pipeline_creation.yml

----
-name: code_review_async_pipeline_creation
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/58542
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/327559
-milestone: '13.11'
-type: development
-group: group::code review
-default_enabled: false

spec/services/merge_requests/refresh_service_spec.rb

@@ -198,7 +198,7 @@ RSpec.describe MergeRequests::RefreshService do
       end
     end
 
-    shared_examples 'Pipelines for merge requests' do
+    context 'Pipelines for merge requests', :sidekiq_inline do
       before do
         stub_ci_pipeline_yaml_file(config)
       end
@@ -364,18 +364,6 @@ RSpec.describe MergeRequests::RefreshService do
       end
     end
 
-    context 'when the code_review_async_pipeline_creation feature flag is on', :sidekiq_inline do
-      it_behaves_like 'Pipelines for merge requests'
-    end
-
-    context 'when the code_review_async_pipeline_creation feature flag is off', :sidekiq_inline do
-      before do
-        stub_feature_flags(code_review_async_pipeline_creation: false)
-      end
-
-      it_behaves_like 'Pipelines for merge requests'
-    end
-
     context 'push to origin repo source branch' do
       let(:refresh_service) { service.new(@project, @user) }
       let(:notification_service) { spy('notification_service') }