fix prediction format issue

Author: TheMichaelHu

tests/system/aiplatform/test_e2e_forecasting.py

@@ -108,6 +108,7 @@ def test_end_to_end_forecasting(self, shared_state, training_job):
                 job_display_name=self._make_display_name(
                     "forecasting-liquor-model"),
                 instances_format="bigquery",
+                predictions_format="csv",
                 machine_type="n1-standard-4",
                 bigquery_source=_PREDICTION_DATASET_BQ_PATH,
                 gcs_destination_prefix=(