Update bigquery.py documentation (#31443)

* Update bigquery.py

fix #31372

* fix lint

sdks/python/apache_beam/io/gcp/bigquery.py

@@ -283,7 +283,8 @@ def compute_table_name(row):
   def chain_after(result):
     try:
       # This works for FILE_LOADS, where we run load and possibly copy jobs.
-      return (result.load_jobid_pairs, result.copy_jobid_pairs) | beam.Flatten()
+      return (result.destination_load_jobid_pairs,
+          result.destination_copy_jobid_pairs) | beam.Flatten()
     except AttributeError:
       # Works for STREAMING_INSERTS, where we return the rows BigQuery rejected
       return result.failed_rows