Bump actions/stale from 5 to 6 (ko-build#826)

Bumps [actions/stale](https://github.com/actions/stale) from 5 to 6.
- [Release notes](https://github.com/actions/stale/releases)
- [Changelog](https://github.com/actions/stale/blob/main/CHANGELOG.md)
- [Commits](actions/stale@v5...v6)

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

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

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

.github/workflows/stale.yaml

@@ -8,7 +8,7 @@ jobs:
   stale:
     runs-on: 'ubuntu-latest'
     steps:
-    - uses: 'actions/stale@v5'
+    - uses: 'actions/stale@v6'
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}