Removed duplicate set_state_cancel on inventory (issue1323)

(transplanted from 10dfa28e1cbe76b7a5f0bf11920ecc2243fecd49)

inventory.py

@@ -65,11 +65,6 @@ class Inventory(OSV):
                     context=context)[0]
         return False
 
-    def set_state_cancel(self, cursor, user, ids, context=None):
-        self.write(cursor, user, ids, {
-            'state': 'cancel',
-            }, context=context)
-
     def set_state_draft(self, cursor, user, inventory_id, context=None):
         self.write(cursor, user, inventory_id, {
             'state': 'draft',