build(deps): 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](actions/download-artifact@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] <[email protected]>

Author: dependabot[bot]

.github/workflows/buildwheel.yml

@@ -90,7 +90,7 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
           allow-prereleases: true
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           path: wheelhouse
           merge-multiple: true
@@ -285,7 +285,7 @@ jobs:
     steps:
         # Downloads all artifacts
       - name: Download release artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           path: wheelhouse
           merge-multiple: true
@@ -318,7 +318,7 @@ jobs:
     steps:
         # Downloads all artifacts
       - name: Download release artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           path: wheelhouse
           merge-multiple: true
@@ -345,7 +345,7 @@ jobs:
       - uses: actions/checkout@v5
 
       - name: Download sdist
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: sdist
           path: dist