Update `grid po version create` man page
This updates the `grid po version create` man page to say "UID" instead
of "UUID".
@@ -65,7 +65,7 @@ OPTIONS
: Specify the organization that owns the purchase order. This option is required.
`--po`
-: Either a UUID or an alternate ID of a purchase order.
+: Either a UID or an alternate ID of a purchase order.
`--service-id`
: The ID of the service the payload should be sent to; required if running on
