Update example to use "@Head"

Otherwise, we get:

> the `uses' attribute must be a path, a Docker image, or owner/repo@ref

(which the documentation implies we shouldn't, but 🤷)

Author: tianon

scripts/github-actions/example-ci.yml

@@ -19,7 +19,7 @@ jobs:
       strategy: ${{ steps.generate-jobs.outputs.strategy }}
     steps:
       - uses: actions/checkout@v3
-      - uses: docker-library/bashbrew
+      - uses: docker-library/bashbrew@HEAD
       - id: generate-jobs
         name: Generate Jobs
         run: |