* and stop setting default values in python operator code, so defaults can be set at the server side.

This issue is just for the PR and questions from maintainers. 
tests/providers/yandex/operators/test_yandexcloud_dataproc.py
def setUp(self):
        dag_id = 'test_dag'
        self.dag = DAG(
            dag_id,
            default_args={
                'owner': 'airflow',
                'start_date': datetime.datetime.today(),
                'end_date': datetime.datetime.today() + datetime.timedelta(days=1),
            },
            schedule_interval='@daily',
        )
    @patch('airflow.providers.yandex.hooks.yandex.YandexCloudBaseHook._get_credentials')
    @patch('airflow.hooks.base.BaseHook.get_connection')
    @patch('yandexcloud._wrappers.dataproc.Dataproc.create_cluster')
    def test_create_cluster(self, create_cluster_mock, *_):