Denote max microversion for Train
This adds a note to the REST API history document to show the highest
microversion in the Train release.
@@ -459,7 +459,7 @@ Add ``project_id`` attribute to response body of list groups with detail,
list group snapshots with detail, show group detail and show group snapshot
detail APIs.
-3.59 (Maximum in Stein)
------------------------
+3.59 (Maximum in Stein and Train)
+---------------------------------
Support volume transfer pagination.
