virsh.pod: Fix typo

Commit id 'c9ffd3ea' updated the descriptions, but pointed at the
wrong place for the pool-define-as (it should have been pool-create-as)

tools/virsh.pod

@@ -3019,7 +3019,7 @@ I<--print-xml> is specified, then print the XML of the pool object
 without defining the pool.  Otherwise, the pool has the specified
 I<type>.
 
-Use the same arguments as B<pool-define-as>.
+Use the same arguments as B<pool-create-as>.
 
 =item B<pool-destroy> I<pool-or-uuid>