Enable 'use_distinct_in_shas_cte' FF by default

This change enables the use_distinct_in_shas_cte feature flag which
improves the performance of PipelinesForMergeRequestFinder.

Changelog: performance

app/finders/ci/pipelines_for_merge_request_finder.rb

@@ -48,7 +48,7 @@ module Ci
     # rubocop: disable CodeReuse/ActiveRecord
     def pipelines_using_cte
       sha_relation = merge_request.all_commits.select(:sha)
-      sha_relation = sha_relation.distinct if Feature.enabled?(:use_distinct_in_shas_cte)
+      sha_relation = sha_relation.distinct if Feature.enabled?(:use_distinct_in_shas_cte, default_enabled: :yaml)
 
       cte = Gitlab::SQL::CTE.new(:shas, sha_relation)
 

config/feature_flags/development/use_distinct_in_shas_cte.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/330586
 milestone: '13.12'
 type: development
 group: group::optimize
-default_enabled: false
+default_enabled: true