Pin GitHub Actions to full-length commit SHAs - #877

Octokit – PATCH /repos/microsoft/Omex/pulls/877 - 403 with id DC01:319CB:57FD7E6:1260EF9F:6A85ABB0 in 147ms

Could not access the resources. Ensure the 'PR_Metrics_Access_Token' secret environment variable has Read and Write access to pull requests (or access to 'repos' if using a Classic PAT).