ci: bump actions/labeler from 5 to 6 (#7789)

Bumps [actions/labeler](https://github.com/actions/labeler) from 5 to 6.
- [Release notes](https://github.com/actions/labeler/releases)
- [Commits](https://github.com/actions/labeler/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/labeler
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/labeler.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository_owner == 'nix-community'
     steps:
-      - uses: actions/labeler@v5
+      - uses: actions/labeler@v6
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           sync-labels: true