⬆️ Update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/tests.yaml

@@ -39,7 +39,7 @@ jobs:
       - name: 🚀 Run pytest
         run: poetry run pytest --cov src tests
       - name: ⬆️ Upload coverage artifact
-        uses: actions/upload-artifact@v5.0.0
+        uses: actions/upload-artifact@v6.0.0
         with:
           include-hidden-files: true
           name: coverage-${{ matrix.python }}