Update configuration path in help message

The default path was already changed with Symfony 4, guess nobody ever found this one!

Author: bobvandevijver

Command/UserPasswordHashCommand.php

@@ -70,7 +70,7 @@ protected function configure()
 Suppose that you have the following security configuration in your application:
 
 <comment>
-# app/config/security.yml
+# config/packages/security.yml
 security:
     password_hashers:
         Symfony\Component\Security\Core\User\InMemoryUser: plaintext