docs: Update Bigquery clustering docstrings (#11232)

Author: ryanyuan

airflow/providers/google/cloud/hooks/bigquery.py

@@ -317,8 +317,8 @@ def create_empty_table(  # pylint: disable=too-many-arguments
                 https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#timePartitioning
         :type time_partitioning: dict
         :param cluster_fields: [Optional] The fields used for clustering.
-            Must be specified with time_partitioning, data in the table will be first
-            partitioned and subsequently clustered.
+            BigQuery supports clustering for both partitioned and
+            non-partitioned tables.
             https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#clustering.fields
         :type cluster_fields: list
         :param view: [Optional] A dictionary containing definition for the view.
@@ -1624,8 +1624,8 @@ def run_load(  # pylint: disable=too-many-locals,too-many-arguments,invalid-name
             partition by field, type and  expiration as per API specifications.
         :type time_partitioning: dict
         :param cluster_fields: Request that the result of this load be stored sorted
-            by one or more columns. This is only available in combination with
-            time_partitioning. The order of columns given determines the sort order.
+            by one or more columns. BigQuery supports clustering for both partitioned and
+            non-partitioned tables. The order of columns given determines the sort order.
         :type cluster_fields: list[str]
         :param encryption_configuration: [Optional] Custom encryption configuration (e.g., Cloud KMS keys).
             **Example**: ::
@@ -2033,8 +2033,8 @@ def run_query(
             partition by field, type and expiration as per API specifications.
         :type time_partitioning: dict
         :param cluster_fields: Request that the result of this query be stored sorted
-            by one or more columns. This is only available in combination with
-            time_partitioning. The order of columns given determines the sort order.
+            by one or more columns. BigQuery supports clustering for both partitioned and
+            non-partitioned tables. The order of columns given determines the sort order.
         :type cluster_fields: list[str]
         :param location: The geographic location of the job. Required except for
             US and EU. See details at

airflow/providers/google/cloud/operators/bigquery.py

@@ -570,8 +570,8 @@ class BigQueryExecuteQueryOperator(BaseOperator):
         partition by field, type and expiration as per API specifications.
     :type time_partitioning: dict
     :param cluster_fields: Request that the result of this query be stored sorted
-        by one or more columns. This is only available in conjunction with
-        time_partitioning. The order of columns given determines the sort order.
+        by one or more columns. BigQuery supports clustering for both partitioned and
+        non-partitioned tables. The order of columns given determines the sort order.
     :type cluster_fields: list[str]
     :param location: The geographic location of the job. Required except for
         US and EU. See details at
@@ -861,8 +861,8 @@ class BigQueryCreateEmptyTableOperator(BaseOperator):
     :param location: The location used for the operation.
     :type location: str
     :param cluster_fields: [Optional] The fields used for clustering.
-            Must be specified with time_partitioning, data in the table will be first
-            partitioned and subsequently clustered.
+            BigQuery supports clustering for both partitioned and
+            non-partitioned tables.
 
             .. seealso::
                 https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#clustering.fields

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

@@ -131,8 +131,8 @@ class GCSToBigQueryOperator(BaseOperator):
         dataset.table$partition.
     :type time_partitioning: dict
     :param cluster_fields: Request that the result of this load be stored sorted
-        by one or more columns. This is only available in conjunction with
-        time_partitioning. The order of columns given determines the sort order.
+        by one or more columns. BigQuery supports clustering for both partitioned and
+        non-partitioned tables. The order of columns given determines the sort order.
         Not applicable for external tables.
     :type cluster_fields: list[str]
     :param autodetect: [Optional] Indicates if we should automatically infer the