Bump actions/download-artifact from 5 to 6 (#1424)

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

---
updated-dependencies:
- dependency-name: actions/download-artifact
  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/compare_screenshots.yml

@@ -13,7 +13,7 @@ jobs:
         run: mkdir -p artifacts
       # If we ever add more artifacts, this is going to break, but it'll be obvious.
       - name: Download screenshot tests
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           path: artifacts
       - name: ls -R