Update docstring indicating required pandas-gbq version.

Author: tswast

doc/source/whatsnew/v0.25.0.rst

@@ -364,7 +364,7 @@ I/O
 - Improved the explanation for the failure when value labels are repeated in Stata dta files and suggested work-arounds (:issue:`25772`)
 - Improved :meth:`pandas.read_stata` and :class:`pandas.io.stata.StataReader` to read incorrectly formatted 118 format files saved by Stata (:issue:`25960`)
 - Fixed bug in loading objects from S3 that contain ``#`` characters in the URL (:issue:`25945`)
-- Updated :func:`read_gbq` to version 0.10.0 of the ``pandas-gbq`` library. Adds ``use_bqstorage_api`` parameter to speed up downloads of large data frames. (:issue:`26104`)
+- Adds ``use_bqstorage_api`` parameter to :func:`read_gbq` to speed up downloads of large data frames. This feature requires version 0.10.0 of the ``pandas-gbq`` library as well as the ``google-cloud-bigquery-storage`` and ``fastavro`` libraries. (:issue:`26104`)
 
 Plotting
 ^^^^^^^^

pandas/io/gbq.py

@@ -113,7 +113,8 @@ def read_gbq(query, project_id=None, index_col=None, col_order=None,
         <https://cloud.google.com/bigquery/docs/access-control#roles>`__
         permission on the project you are billing queries to.
 
-        This feature requires the ``google-cloud-bigquery-storage`` and
+        This feature requires version 0.10.0 or later of the ``pandas-gbq``
+        package. It also requires the ``google-cloud-bigquery-storage`` and
         ``fastavro`` packages.
 
         .. versionadded:: 0.25.0