github-actions(deps): bump actions/upload-artifact from 2 to 4

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 2 to 4.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v2...v4)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/diagnostics.yml

@@ -78,7 +78,7 @@ jobs:
         run: ./vendor/bin/phpcq run -v ${{ matrix.output }}
 
       - name: Upload build directory to artifact
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         if: ${{ success() }} || ${{ failure() }}
         with:
           name: phpcq-builds-php-${{ matrix.php }}