[mergebot] Add return on force (#79450)

See title
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79450
Approved by: https://github.com/clee2000, https://github.com/janeyx99
diff --git a/.github/scripts/trymerge.py b/.github/scripts/trymerge.py
index 8014cb3..61234e3 100755
--- a/.github/scripts/trymerge.py
+++ b/.github/scripts/trymerge.py
@@ -930,7 +930,7 @@
     pr = GitHubPR(org, project, pr_num)
     initial_commit_sha = pr.last_commit()['oid']
     if force:
-        pr.merge_into(repo, dry_run=dry_run, force=force, comment_id=comment_id)
+        return pr.merge_into(repo, dry_run=dry_run, force=force, comment_id=comment_id)
     if (datetime.utcnow() - pr.last_pushed_at()).days > stale_pr_days:
         raise RuntimeError("This PR is too stale; the last push date was more than 3 days ago. Please rebase and try again.")