[Security] Remove unneeded and invalid use statement

src/Symfony/Component/Security/Http/Firewall.php

@@ -12,7 +12,6 @@
 namespace Symfony\Component\Security\Http;
 
 use Symfony\Component\HttpKernel\HttpKernelInterface;
-use Symfony\Component\HttpKernel\Events;
 use Symfony\Component\HttpKernel\Event\GetResponseEvent;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;