Bump actions/github-script from 4 to 8

Bumps [actions/github-script](https://github.com/actions/github-script) from 4 to 8.
- [Release notes](https://github.com/actions/github-script/releases)
- [Commits](https://github.com/actions/github-script/compare/v4...v8)

---
updated-dependencies:
- dependency-name: actions/github-script
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/onpr_automerge.yaml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - name: Add the automerge label
         if: ${{ github.event.issue.pull_request && contains(github.event.comment.body, '/automerge') }}
-        uses: actions/github-script@v4
+        uses: actions/github-script@v8
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}
           script: |