Bump actions/download-artifact from 5 to 6

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>

.github/workflows/build.yml

@@ -122,7 +122,7 @@ jobs:
     needs: [build, make_sdist]
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/download-artifact@v5
+    - uses: actions/download-artifact@v6
       with:
         merge-multiple: true
         path: dist
@@ -139,7 +139,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'release' && github.event.action == 'published'
     steps:
-    - uses: actions/download-artifact@v5
+    - uses: actions/download-artifact@v6
       with:
         merge-multiple: true
         path: dist