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/on-push.yml

@@ -43,7 +43,7 @@ jobs:
     - name: Run acceptance tests
       run: |
         inv atest -z True
-    - uses: actions/upload-artifact@v5
+    - uses: actions/upload-artifact@v6
       if: ${{ always() }}
       with:
         name: Test_results_${{ matrix.python-version }}_${{ matrix.rf-version }}