ci: remove continue-on-error from stop/start lifecycle test

The microk8s flakiness fix (canonical/microk8s#5546) has merged, so the
stop/start lifecycle test no longer needs to tolerate failures.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: louiseschmidtgen

.github/workflows/microk8s-integration.yaml

@@ -91,8 +91,6 @@ jobs:
           sudo -E python -m pytest -rA -s tests/test-simple.py -k "not test_microk8s_stop_start"
 
       - name: Run stop/start lifecycle test
-        # canonical/microk8s#5546 fixes the flakiness; continue-on-error until it merges
-        continue-on-error: true
         run: |
           cd microk8s
           sudo -E python -m pytest -rA -s tests/test-simple.py -k "test_microk8s_stop_start"