Bump actions/upload-artifact from 4 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v6)

---
updated-dependencies:
- dependency-name: actions/upload-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/docs.yml

@@ -44,7 +44,7 @@ jobs:
           rm docs/build/html/.buildinfo
 
       - name: Upload documentation
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: sphinx-docs
           path: docs/build/html

.github/workflows/main.yml

@@ -79,7 +79,7 @@ jobs:
         ls -la dist
     - name: Upload package
       if: github.event_name == 'push'
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
         name: python-packages
         path: dist