Remove update_target_approvers feature flag

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/238977

ee/app/services/ee/merge_requests/refresh_service.rb

@@ -37,17 +37,13 @@ module EE
       end
 
       def update_approvers_for_target_branch_merge_requests
-        if update_target_approvers_features_enabled? && branch_protected? && code_owners_updated?
+        if project.feature_available?(:code_owners) && branch_protected? && code_owners_updated?
           merge_requests_for_target_branch.each do |merge_request|
             ::MergeRequests::SyncCodeOwnerApprovalRules.new(merge_request).execute unless merge_request.on_train?
           end
         end
       end
 
-      def update_target_approvers_features_enabled?
-        ::Feature.enabled?(:update_target_approvers, project) && project.feature_available?(:code_owners)
-      end
-
       def branch_protected?
         project.branch_requires_code_owner_approval?(push.branch_name)
       end

ee/changelogs/unreleased/remove_update_target_approvers_feature_flag.yml

+---
+title: Update merge requests approvers when code owners is updated
+merge_request: 45290
+author:
+type: added

ee/config/feature_flags/development/update_target_approvers.yml

----
-name: update_target_approvers
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38575
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/238977
-group: group::source code
-type: development
-default_enabled: false

ee/spec/services/ee/merge_requests/refresh_service_spec.rb

@@ -75,13 +75,11 @@ RSpec.describe MergeRequests::RefreshService do
       subject { service.execute(oldrev, newrev, "refs/heads/master") }
 
       let(:enable_code_owner) { true }
-      let(:enable_target_approvers) { true }
       let!(:protected_branch) { create(:protected_branch, name: 'master', project: project, code_owner_approval_required: true) }
       let(:newrev) { TestEnv::BRANCH_SHA['with-codeowners'] }
 
       before do
-        stub_feature_flags(update_target_approvers: enable_target_approvers, code_owners: enable_code_owner)
-        stub_licensed_features(code_owner_approval_required: true)
+        stub_licensed_features(code_owner_approval_required: true, code_owners: enable_code_owner)
       end
 
       context 'when the feature flags are enabled' do
@@ -133,14 +131,8 @@ RSpec.describe MergeRequests::RefreshService do
         end
       end
 
-      context 'when update_target_approvers is disabled' do
-        let(:enable_code_owner) { false }
-
-        it_behaves_like 'does not refresh the code owner rules'
-      end
-
       context 'when code_owners is disabled' do
-        let(:enable_target_approvers) { false }
+        let(:enable_code_owner) { false }
 
         it_behaves_like 'does not refresh the code owner rules'
       end