Bump actions/upload-artifact from 3 to 4 (#12)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...v4)

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

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

.github/workflows/sync-labels.yml

@@ -70,7 +70,7 @@ jobs:
           file-url: https://raw.githubusercontent.com/107-systems/.github/main/workflow-templates/assets/sync-labels/${{ matrix.filename }}
 
       - name: Pass configuration files to next job via workflow artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           path: |
             *.yaml