Skip stale check when facebook-github-bot is merging (#79572)
# Summary
ShipIt jobs triggered by co-development workflows are failing to merge PRs due to stale checks. This diff skips the stale check when merge is triggered by `facebook-github-bot`.
Sample merge failure: https://github.com/pytorch/pytorch/pull/78654#issuecomment-1155607617
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79572
Approved by: https://github.com/bigfootjon, https://github.com/seemethere, https://github.com/malfet
