Add comment about labeling configuration to that workflow (#17797)

Author: JamesMGreene

.github/workflows/auto-label-prs.yml

@@ -1,4 +1,5 @@
 name: Auto label Pull Requests
+
 on:
   pull_request:
 
@@ -7,6 +8,7 @@ jobs:
     if: github.repository == 'github/docs-internal'
     runs-on: ubuntu-latest
     steps:
+      # See labeling configuration in the `.github/labeler.yml` file
       - uses: actions/labeler@5f867a63be70efff62b767459b009290364495eb
         with:
           repo-token: '${{ secrets.GITHUB_TOKEN }}'