Bump actions/stale from 6 to 9

Bumps [actions/stale](https://github.com/actions/stale) from 6 to 9.
- [Release notes](https://github.com/actions/stale/releases)
- [Changelog](https://github.com/actions/stale/blob/main/CHANGELOG.md)
- [Commits](actions/stale@v6...v9)

---
updated-dependencies:
- dependency-name: actions/stale
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/stale.yml

@@ -14,7 +14,7 @@ jobs:
       pull-requests: write  # for actions/stale to close stale PRs
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v6
+      - uses: actions/stale@v9
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           stale-issue-message: 'This issue is stale, because it has been open for 45 days with no activity. Remove the stale label or comment, or this will be closed in 7 days.'