Bump actions/download-artifact from 6 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 6 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v6...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/wheels.yml

@@ -105,7 +105,7 @@ jobs:
     if: github.event_name == 'release' && github.event.action == 'published'
     steps:
       - name: Download artifacts
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v8
         with:
           # unpacks all CIBW artifacts into dist/
           pattern: cibw-*