Bump actions/upload-artifact in /.github/workflows in the actions group

Bumps the actions group in /.github/workflows with 1 update: [actions/upload-artifact](https://github.com/actions/upload-artifact).


Updates `actions/upload-artifact` from 5 to 6
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/pytest.yml

@@ -30,7 +30,7 @@ jobs:
     - name: Test with pytest
       run: |
         pytest --mpl --mpl-results-path=results --mpl-generate-summary=html
-    - uses: actions/upload-artifact@v5
+    - uses: actions/upload-artifact@v6
       if: failure()
       with:
         name: pytest-${{ matrix.python-version }}-results