Enable optimimal API v3/repos/{full-path}/events

Removing the feature flag added in
44777e66

https://gitlab.com/gitlab-org/gitlab/-/issues/321839
https://gitlab.com/gitlab-org/gitlab/-/issues/322059

changelogs/unreleased/322059-remove-api_v3_repos_events_optimization-flag.yml

+---
+title: Fix N+1 queries in api/v3/repos/:namespace/:project/events endpoint
+merge_request: 55442
+author:
+type: performance

config/feature_flags/development/api_v3_repos_events_optimization.yml

----
-name: api_v3_repos_events_optimization
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/54618
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/322059
-milestone: '13.10'
-type: development
-group: group::ecosystem
-default_enabled: false

lib/api/v3/github.rb

@@ -199,10 +199,7 @@ module API
           user_project = find_project_with_access(params)
 
           merge_requests = authorized_merge_requests_for_project(user_project)
-
-          if Feature.enabled?(:api_v3_repos_events_optimization, user_project)
           merge_requests = merge_requests.preload(:author, :assignees, :metrics, source_project: :namespace, target_project: :namespace)
-          end
 
           present paginate(merge_requests), with: ::API::Github::Entities::PullRequestEvent
         end

spec/requests/api/v3/github_spec.rb

@@ -187,23 +187,6 @@ RSpec.describe API::V3::Github do
         expect { jira_get v3_api(events_path, user) }.not_to exceed_all_query_limit(control_count)
       end
 
-      context 'with `api_v3_repos_events_optimization` feature flag disabled' do
-        before do
-          stub_feature_flags(api_v3_repos_events_optimization: false)
-        end
-
-        it 'falls back to less optimal query performance' do
-          create(:merge_request, source_project: project)
-          source_project = fork_project(project, nil, repository: true)
-
-          control_count = ActiveRecord::QueryRecorder.new(skip_cached: false) { jira_get v3_api(events_path, user) }.count
-
-          create_list(:merge_request, 2, :unique_branches, source_project: source_project, target_project: project)
-
-          expect { jira_get v3_api(events_path, user) }.to exceed_all_query_limit(control_count)
-        end
-      end
-
       context 'if there are more merge requests' do
         let!(:merge_request) { create(:merge_request, id: 10000, source_project: project, target_project: project, author: user) }
         let!(:merge_request2) { create(:merge_request, id: 10001, source_project: project, source_branch: generate(:branch), target_project: project, author: user) }