Use project's group as actor for remove_comment_close_reopen flag

When viewing an issue or merge request, the `@group` ivar isn't
present. For the flag to work for group, we get the `@project`'s
group instead if `@group` isn't present.

app/controllers/concerns/comment_and_close_flag.rb

@@ -5,7 +5,7 @@ module CommentAndCloseFlag
 
   included do
     before_action do
-      push_frontend_feature_flag(:remove_comment_close_reopen, @group)
+      push_frontend_feature_flag(:remove_comment_close_reopen, @group || @project&.group)
     end
   end
 end