Update README.md

Fixing Kernel namespace, see https://github.com/phpstan/phpstan-symfony#console-command-analysis

Author: ThomasLandauer

README.md

@@ -72,7 +72,7 @@ For example, in a Symfony project, `object-manager.php` would look something lik
 <?php
 
 require dirname(__DIR__).'/../config/bootstrap.php';
-$kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER['APP_DEBUG']);
+$kernel = new \App\Kernel($_SERVER['APP_ENV'], (bool) $_SERVER['APP_DEBUG']);
 $kernel->boot();
 return $kernel->getContainer()->get('doctrine')->getManager();
 ```