Bump actions/download-artifact from 4 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v4...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/pypi-publish.yml

@@ -85,7 +85,7 @@ jobs:
     if: github.event_name == 'release' && github.event.action == 'published'
     steps:
     - name: Retrieve distributions
-      uses: actions/download-artifact@v4
+      uses: actions/download-artifact@v6
       with:
         name: artifact
         path: dist