Remove check for at least one schema in GCSToBigquery (#18150)

For the case when updating an existing table or insert data to a particular partition, no schema is needed.
Autodetect doesn't always work, e.g. cannot distinguish partition correctly. Other options requires forking the schema to airflow.

airflow/providers/google/cloud/transfers/gcs_to_bigquery.py

@@ -20,7 +20,6 @@
 import json
 from typing import Optional, Sequence, Union
 
-from airflow.exceptions import AirflowException
 from airflow.models import BaseOperator
 from airflow.providers.google.cloud.hooks.bigquery import BigQueryHook
 from airflow.providers.google.cloud.hooks.gcs import GCSHook
@@ -274,10 +273,6 @@ def execute(self, context):
                     object_name=self.schema_object,
                 )
                 schema_fields = json.loads(blob.decode("utf-8"))
-            elif self.schema_object is None and self.autodetect is False:
-                raise AirflowException(
-                    'At least one of `schema_fields`, `schema_object`, or `autodetect` must be passed.'
-                )
             else:
                 schema_fields = None