Update actions/upload-artifact action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Run tests and collect coverage
         run: pytest --timeout=300 --junitxml=junit/test-results.xml --cov=relay --cov=tests --cov-report=xml --cov-report=html
       - name: Upload pytest test results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: pytest-results
           path: junit/test-results.xml