[AIRFLOW-5152] Change back autodetect default value from False to True in GoogleCloudStorageToBigQueryOperator. (apache#5771)

Set autodetect default value from false to be true to avoid breaking downstream
services using GoogleCloudStorageToBigQueryOperator but not aware of the newly
added autodetect field.

This is to fix the current regression introduced by apache#3880

(cherry picked from commit 462ab88)

Author: bingqinzhou

airflow/contrib/operators/gcs_to_bq.py

@@ -127,7 +127,7 @@ class GoogleCloudStorageToBigQueryOperator(BaseOperator):
         Not applicable for external tables.
     :type cluster_fields: list[str]
     :param autodetect: [Optional] Indicates if we should automatically infer the
-        options and schema for CSV and JSON sources. (Default: ``False``).
+        options and schema for CSV and JSON sources. (Default: ``True``).
         Parameter must be setted to True if 'schema_fields' and 'schema_object' are undefined.
         It is suggested to set to True if table are create outside of Airflow.
     :type autodetect: bool
@@ -171,7 +171,7 @@ def __init__(self,
                  external_table=False,
                  time_partitioning=None,
                  cluster_fields=None,
-                 autodetect=False,
+                 autodetect=True,
                  encryption_configuration=None,
                  *args, **kwargs):