ci: introduced timeouts

The default value is around 6hours. This drastically reduces it, so that
infinite loops won't make the CI take that long.

.github/workflows/tests.yml

@@ -35,6 +35,7 @@ jobs:
       run: make karapace/version.py
 
     - name: Execute unit-tests
+      timeout-minutes: 2
       run: python3 -m pytest -s -vvv tests/unit/
 
     - name: Execute integration-tests