Remove limit_epic_groups_query flag

config/feature_flags/development/limit_epic_groups_query.yml

----
-name: limit_epic_groups_query
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/59360
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/327624
-milestone: '13.12'
-type: development
-group: group::product planning
-default_enabled: false

ee/app/finders/epics_finder.rb

@@ -102,10 +102,8 @@ class EpicsFinder < IssuableFinder
       # all epics in all subgroups
       next groups if can_read_all_epics_in_related_groups?(groups, include_confidential: false)
 
-      if Feature.enabled?(:limit_epic_groups_query, group)
-        next groups.public_to_user unless current_user
-        next groups.public_to_user(current_user) unless groups.user_is_member(current_user).exists?
-      end
+      next groups.public_to_user unless current_user
+      next groups.public_to_user(current_user) unless groups.user_is_member(current_user).exists?
 
       # when traversal ids are enabled, we could avoid N+1 issue
       # by taking all public groups plus groups where user is member

ee/changelogs/unreleased/ff-epic-finder.yml

+---
+title: Optimize number of SQL queries when listing epics.
+merge_request: 61372
+author:
+type: performance

ee/spec/finders/epics_finder_spec.rb

@@ -570,16 +570,6 @@ RSpec.describe EpicsFinder do
             end
 
             it_behaves_like 'avoids N+1 queries'
-
-            context 'when limit_epic_groups_query is disabled' do
-              before do
-                stub_feature_flags(limit_epic_groups_query: false)
-              end
-
-              it 'returns only public epics' do
-                expect(execute).to match_array([base_epic2, public_epic1, internal_epic])
-              end
-            end
           end
 
           context 'when skip_visibility_check is true' do