### Body

Currently `start_date` is mandatory parameter.
For DAGs with `schedule=None` we can relax this requirement as no scheduling calculation needed so the `start_date` parameter isn't used.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
self.sensor._get_gcs_hook()
        mock_hook.assert_called_once_with(
            gcp_conn_id=TEST_GCP_CONN_ID,
            impersonation_chain=TEST_IMPERSONATION_CHAIN,
        )
        assert mock_hook.return_value == self.sensor.hook
    @pytest.mark.parametrize(
        "soft_fail, expected_exception", ((False, AirflowException), (True, AirflowSkipException))
    )
    @mock.patch("airflow.providers.google.cloud.sensors.gcs.get_time", mock_time)
    def test_files_deleted_between_pokes_throw_error(self, soft_fail, expected_exception):