Revert: Revert import change in read_gbq_colab benchmark

This reverts the import path for the benchmark utils to 'benchmark.utils' to address concerns about google3 imports.

Author: shuoweil

bigframes/dataframe.py

@@ -1930,9 +1930,10 @@ def to_pandas_batches(
                 over the default size limit of 10 GB.
 
         Returns:
-            An iterable of smaller dataframes which combine to
-            form the original dataframe. Results stream from bigquery,
-            see https://cloud.google.com/python/docs/reference/bigquery/latest/google.cloud.bigquery.table.RowIterator#google_cloud_bigquery_table_RowIterator_to_arrow_iterable
+            Iterable[pandas.DataFrame]:
+                An iterable of smaller dataframes which combine to
+                form the original dataframe. Results stream from bigquery,
+                see https://cloud.google.com/python/docs/reference/bigquery/latest/google.cloud.bigquery.table.RowIterator#google_cloud_bigquery_table_RowIterator_to_arrow_iterabl
         """
         return self._to_pandas_batches(
             page_size=page_size,