erp5_free_subscription: fix unsubscribe URL

bt5/erp5_free_subscription/SkinTemplateItem/portal_skins/erp5_free_subscription/NotificationMessage_getSubstitutionMappingDictFromEvent.xml

@@ -87,7 +87,7 @@ def getSubstitutionMappingDict():\n
   hmac = portal.Base_getHMACHexdigest(key=portal.Base_getEventHMACKey(), message=event_value.getId())\n
   kw["image_parameters"] = "/Base_openEvent?id=%s&hash=%s" %(event_value.getId(), hmac)\n
   kw["newsletter_parameters"] = "/Base_readEvent?id=%s&hash=%s" %(event_value.getId(), hmac)\n
-  kw["unsubscribe_parameters"] = "/Base_unsubscribe?id=%s&hash=%s" %(event_value.getId(), hmac)\n
+  kw["unsubscribe_parameters"] = "/Base_unsubscribeFromEvent?id=%s&hash=%s" %(event_value.getId(), hmac)\n
 \n
   return kw\n
 \n