Bump actions/stale from 4 to 9 in /.github/workflows

Bumps [actions/stale](https://github.com/actions/stale) from 4 to 9.
- [Release notes](https://github.com/actions/stale/releases)
- [Changelog](https://github.com/actions/stale/blob/main/CHANGELOG.md)
- [Commits](actions/stale@v4...v9)

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

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

Author: dependabot[bot]

.github/workflows/stale.yml

@@ -6,7 +6,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v4
+      - uses: actions/stale@v9
         with:
           stale-issue-message: 'This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution!'
           close-issue-message: 'Please reopen this issue once you have made the required changes. If you need help, feel free to ask in our [Discord](https://the-algorithms.com/discord) server or ping one of the maintainers here. Thank you for your contribution!'