Bump actions/upload-artifact from 4 to 5

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 5.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v5)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/pr_validation.yaml

@@ -138,7 +138,7 @@ jobs:
         if: runner.os == 'Linux'
 
       - name: Upload flattened screenshots
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: playwright-screenshots-${{ matrix.os == 'windows-latest' && 'windows' || 'linux' }}-${{ github.run_id }}
           path: flat-screenshots/