Try using as many workers as available for test workflow

Not sure why this is set to 1 originally

Author: cderici

.github/workflows/test.yaml

@@ -102,4 +102,4 @@ jobs:
         run: pip install tox
       - name: Run integration
         # Force one single concurrent test
-        run: tox -e integration -- -n 1
+        run: tox -e integration