infra: merge queue allowed (#28641)

.github/workflows/check_diffs.yml

@@ -5,6 +5,7 @@ on:
   push:
     branches: [master]
   pull_request:
+  merge_group:
 
 # If another push to the same PR or branch happens while this workflow is still running,
 # cancel the earlier run in favor of the next run.