added missing import

Author: deluxetom

Tests/Functional/app/CustomGuardAuthenticator/security.php

@@ -9,6 +9,8 @@
  * file that was distributed with this source code.
  */
 
+use Symfony\Component\HttpKernel\Kernel;
+
 $securityConfig = [
     'providers' => [
         'in_memory' => [