Update append_rows_with_arrow.py

Author: AlexZMLyu

packages/google-cloud-bigquery-storage/samples/pyarrow/append_rows_with_arrow.py

@@ -223,6 +223,7 @@ def verify_result(client, table, futures):
     assert query_result.iloc[0, 0] >= TABLE_LENGTH
 
     # Verify that table was split into multiple requests.
+    print(len(futures))
     assert len(futures) == 2