Merge branch '352670-use-to_a-to-avoid-gc-bug-in-ruby' into 'master'

Explicitly call #to_a to avoid potential GC bug

See merge request gitlab-org/gitlab!81948

lib/gitlab/gitaly_client/commit_service.rb

@@ -212,7 +212,7 @@ module Gitlab
         )
 
         response = GitalyClient.call(@repository.storage, :diff_service, :diff_stats, request, timeout: GitalyClient.medium_timeout)
-        response.flat_map(&:stats)
+        response.flat_map { |rsp| rsp.stats.to_a }
       end
 
       def find_changed_paths(commits)