[ticket/12742] Remove unneeded sort of users

It doesn't matter which user will get the notification first so we shouldn't
sort the users array.

PHPBB3-12742

phpBB/phpbb/notification/type/base.php

@@ -550,7 +550,6 @@ abstract class base implements \phpbb\notification\type\type_interface
 		}
 
 		$users = array_unique($users);
-		sort($users);
 
 		$auth_read = $this->auth->acl_get_list($users, 'f_read', $forum_id);