Bump actions/upload-artifact from 5 to 6

Bumps [actions/upload-artifact](https://github.com/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
...

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

Author: dependabot[bot]

.github/workflows/bnf-pytest.yml

@@ -61,7 +61,7 @@ jobs:
         working-directory: bnf
         run: uv build
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: dist
           path: bnf/dist/*.whl

.github/workflows/pytest.yml

@@ -60,7 +60,7 @@ jobs:
       - name: build wheels
         run: python -m cibuildwheel
 
-      - uses: actions/upload-artifact@v5
+      - uses: actions/upload-artifact@v6
         with:
           name: wheels-${{ matrix.os }}
           path: wheelhouse/*.whl