Update to FOSUserBundle 3.1

Also remove some deprecation from Symfony.
Use `LegacyEventDispatcherProxy` to handle Symfony 4 dispatch from FOSUser

src/Wallabag/UserBundle/Controller/ManageController.php

@@ -11,6 +11,7 @@ use Pagerfanta\Pagerfanta;
 use Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Google\GoogleAuthenticatorInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy;
 use Symfony\Component\Form\Form;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -49,7 +50,7 @@ class ManageController extends Controller
 
             // dispatch a created event so the associated config will be created
             $event = new UserEvent($user, $request);
-            $this->get(EventDispatcherInterface::class)->dispatch(FOSUserEvents::USER_CREATED, $event);
+            LegacyEventDispatcherProxy::decorate($this->get(EventDispatcherInterface::class))->dispatch($event, FOSUserEvents::USER_CREATED);
 
             $this->get(SessionInterface::class)->getFlashBag()->add(
                 'notice',