Do not play with next_date

Changing next_date in certain case cause simulation to create compensation. As compensation is disallowed in commit a2f258eea0a8e58929b61e2ca2ee753c623cf510, changing nexte_date in this cause undesired behavior because of wrong date.

product/ERP5/Document/SubscriptionItem.py

@@ -150,8 +150,6 @@ class SubscriptionItem(Item, CompositionMixin, MovementGeneratorMixin,
         id_index = 0
         while current_date < stop_date:
           next_date = self.getNextPeriodicalDate(current_date)
-          if next_date > stop_date:
-            next_date = stop_date
           generated_movement = newTempMovement(self, 'subscription_%s' % id_index)
           generated_movement._edit(  aggregate_value=self,
                                      resource=resource,