Set sticky data_consistency for UpdateMergeRequestsWorker

Currently ~40% of UpdateMergeRequestsWorker jobs perform 0 writes
so it makes sense to use sticky option to reduce the load on primary.

app/workers/update_merge_requests_worker.rb

@@ -3,7 +3,7 @@
 class UpdateMergeRequestsWorker # rubocop:disable Scalability/IdempotentWorker
   include ApplicationWorker
 
-  data_consistency :always
+  data_consistency :sticky, feature_flag: :update_merge_request_worker_sticky
 
   sidekiq_options retry: 3
 

config/feature_flags/worker/update_merge_request_worker_sticky.yml

+---
+name: update_merge_request_worker_sticky
+feature_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/403184
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/171352
+rollout_issue_url:
+milestone: '17.6'
+group: group::code review
+type: worker
+default_enabled: false