v2.26.0: Use `commit` as `head_sha` to reduce number of API calls (#227)

* Use `commit` as `head_sha` to reduce number of API calls

Less results -> less pagination -> less API calls.
Maybe a bit faster even.

https://octokit.github.io/rest.js/v19#actions-list-workflow-runs

* Add CI check for commit

* Use event head_sha