fix typo

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@20289 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/PropertySheet/Order.py

@@ -70,7 +70,7 @@ class Order:
 
   _constraints = (
     { 'id'            : 'applied_rule',
-      'description'   : 'There must at most one Applied Rule using this order',
+      'description'   : 'There must be at most one Applied Rule using this order',
       'type'          : 'CategoryRelatedMembershipArity',
       'min_arity'     : '0',
       'max_arity'     : '1',