Mention compute API 2.50 in openstack quota show --class

There is a bug in the compute API until microversion 2.50
where the server-groups and server-group-members class
quota fields aren't returned. This just mentions that
microversion in the command help text.

Change-Id: I029a614a922d642c578618c478c4d0a29a394fc2
Task: 21490
Story: 2002194

Author: mriedem

doc/source/cli/command-objects/quota.rst

@@ -244,7 +244,9 @@ Set quotas for class
 quota show
 ----------
 
-Show quotas for project or class
+Show quotas for project or class. Specify ``--os-compute-api-version 2.50`` or
+higher to see ``server-groups`` and ``server-group-members`` output for a given
+quota class.
 
 .. program:: quota show
 .. code:: bash

openstackclient/common/quota.py

@@ -570,7 +570,10 @@ def take_action(self, parsed_args):
 
 
 class ShowQuota(command.ShowOne, BaseQuota):
-    _description = _("Show quotas for project or class")
+    _description = _(
+        "Show quotas for project or class. Specify "
+        "``--os-compute-api-version 2.50`` or higher to see ``server-groups`` "
+        "and ``server-group-members`` output for a given quota class.")
 
     def get_parser(self, prog_name):
         parser = super(ShowQuota, self).get_parser(prog_name)