Temporarily skip integration test

This test (test_application.py::test_upgrade_local_charm) has been
messing us up for a while by constantly failing our CI with a known
issue :

juju.errors.JujuAPIError: cannot upgrade application "ubuntu" to charm
"local:focal/ubuntu-0": required storage "files" removedq

This temporary change is to get the CI green to make sure we
spot failures due to changes in PRs.

Author: cderici

tests/integration/test_application.py

@@ -180,6 +180,8 @@ async def test_upgrade_charm_switch_channel(event_loop):
 @base.bootstrapped
 @pytest.mark.asyncio
 async def test_upgrade_local_charm(event_loop):
+    # Skip temporarily due to a known problem:
+    pytest.skip('cannot upgrade application "ubuntu" to charm "local:focal/ubuntu-0": required storage "files" removed')
     async with base.CleanModel() as model:
         tests_dir = Path(__file__).absolute().parent
         charm_path = tests_dir / 'upgrade-charm'