Remove FF ci_root_ancestor_for_pipeline_family

app/models/ci/pipeline.rb

@@ -851,15 +851,9 @@ module Ci
     end
 
     def same_family_pipeline_ids
-      if Feature.enabled?(:ci_root_ancestor_for_pipeline_family, project, default_enabled: false)
-        ::Gitlab::Ci::PipelineObjectHierarchy.new(
-          self.class.where(id: root_ancestor), options: { same_project: true }
-        ).base_and_descendants.select(:id)
-      else
-        ::Gitlab::Ci::PipelineObjectHierarchy.new(
-          base_and_ancestors(same_project: true), options: { same_project: true }
-        ).base_and_descendants.select(:id)
-      end
+      ::Gitlab::Ci::PipelineObjectHierarchy.new(
+        self.class.where(id: root_ancestor), options: { same_project: true }
+      ).base_and_descendants.select(:id)
     end
 
     def build_with_artifacts_in_self_and_descendants(name)

changelogs/unreleased/remove-ff-ci-root-ancestor-for-pipeline-family.yml

+---
+title: Improve query that finds all pipelines in the same family
+merge_request: 49240
+author:
+type: performance

config/feature_flags/development/ci_root_ancestor_for_pipeline_family.yml

----
-name: ci_root_ancestor_for_pipeline_family
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46575 
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/287812 
-milestone: '13.7'
-type: development
-group: group::continuous integration
-default_enabled: false