There seems to be a bug in actionlint when running it on multiple files
(reported here: https://github.com/rhysd/actionlint/issues/173). This
was causing CI to be green even though there are local linter failures.

This PR:
1. Changes our usage of actionlint to work around the aforementioned
bug.
2. Fixes the linter failures introduced
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81119
Approved by: https://github.com/malfet