Remove project authorizations API FF

This change removes the already default-enabled feature flag
(sort_by_project_users_by_project_authorizations_user_id) for
improving the performance of the project authorizations API.

Changelog: other

config/feature_flags/development/sort_by_project_users_by_project_authorizations_user_id.yml

----
-name: sort_by_project_users_by_project_authorizations_user_id
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64528
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/334167
-milestone: '14.1'
-type: development
-group: group::optimize
-default_enabled: true

lib/api/projects.rb

@@ -658,10 +658,7 @@ module API
         users = DeclarativePolicy.subject_scope { user_project.team.users }
         users = users.search(params[:search]) if params[:search].present?
         users = users.where_not_in(params[:skip_users]) if params[:skip_users].present?
-
-        if Feature.enabled?(:sort_by_project_users_by_project_authorizations_user_id, user_project, default_enabled: :yaml)
         users = users.order('project_authorizations.user_id' => :asc) # rubocop: disable CodeReuse/ActiveRecord
-        end
 
         present paginate(users), with: Entities::UserBasic
       end

spec/requests/api/projects_spec.rb

@@ -2684,29 +2684,12 @@ RSpec.describe API::Projects do
 
     context 'when authenticated' do
       context 'valid request' do
-        context 'when sort_by_project_authorizations_user_id FF is off' do
-          before do
-            stub_feature_flags(sort_by_project_users_by_project_authorizations_user_id: false)
-          end
-
         it_behaves_like 'project users response' do
           let(:project) { project4 }
           let(:current_user) { user4 }
         end
       end
 
-        context 'when sort_by_project_authorizations_user_id FF is on' do
-          before do
-            stub_feature_flags(sort_by_project_users_by_project_authorizations_user_id: true)
-          end
-
-          it_behaves_like 'project users response' do
-            let(:project) { project4 }
-            let(:current_user) { user4 }
-          end
-        end
-      end
-
       it 'returns a 404 error if not found' do
         get api("/projects/#{non_existing_record_id}/users", user)