workflows: update pr-auditor workflow
Created by: bobheadxi
This pull request updates the pr-auditor workflow.
Test plan: We have tested the code itself in https://github.com/sourcegraph/sourcegraph/tree/main/dev/pr-auditor, and the pr-auditor action should continue working as expected on this pull request.
Created by Sourcegraph batch change robert/pr-auditor-patch-06-16.
