Add file_identifier_hash feature flag to frontend

app/controllers/projects/merge_requests_controller.rb

@@ -34,6 +34,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     push_frontend_feature_flag(:merge_ref_head_comments, @project)
     push_frontend_feature_flag(:mr_commit_neighbor_nav, @project, default_enabled: true)
     push_frontend_feature_flag(:multiline_comments, @project)
+    push_frontend_feature_flag(:file_identifier_hash)
   end
 
   before_action do