Add versionchanged to read_gbq dialect.

Author: tswast

pandas/io/gbq.py

@@ -80,6 +80,8 @@ def read_gbq(query, project_id=None, index_col=None, col_order=None,
             compliant with the SQL 2011 standard. For more information
             see `BigQuery Standard SQL Reference
             <https://cloud.google.com/bigquery/docs/reference/standard-sql/>`__.
+
+        .. versionchanged:: 0.24.0
     location : str, optional
         Location where the query job should run. See the `BigQuery locations
         documentation