build(deps): bump actions/labeler from 5 to 6

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>

.github/workflows/labels.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-24.04
     if: github.repository_owner == 'NixOS'
     steps:
-    - uses: actions/labeler@v5
+    - uses: actions/labeler@v6
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         sync-labels: false