Bump actions/stale from 8.0.0 to 9.0.0 (spiffe#4722)

Bumps [actions/stale](https://github.com/actions/stale) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/actions/stale/releases)
- [Changelog](https://github.com/actions/stale/blob/main/CHANGELOG.md)
- [Commits](actions/stale@1160a22...28ca103)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/stalebot.yaml

@@ -11,7 +11,7 @@ jobs:
       issues: write
       pull-requests: write
     steps:
-    - uses: actions/stale@1160a2240286f5da8ec72b1c0816ce2481aabf84 # v8.0.0
+    - uses: actions/stale@28ca1036281a5e5922ead5184a1bbf96e5fc984e # v9.0.0
       with:
         days-before-issue-stale: 365 # 1 year
         days-before-issue-close: 30