Replace Controller with AbstractController

As of Symfony 4.2 Controller is depreciated in favor of AbstractController. To reflect this update I tweaked the section of getting parameter, as it slightly changed, and getParameter is no longer there on the container,

Author: krisdante

service_container.rst

@@ -534,8 +534,8 @@ You can also fetch parameters directly from the container::
     {
         // ...
 
-        // this ONLY works if you extend the base Controller
-        $adminEmail = $this->container->getParameter('admin_email');
+        // this ONLY works if you extend the base AbstractController
+        $adminEmail = $this->container->get('parameter_bag')->get('admin_email');
 
         // or a shorter way!
         // $adminEmail = $this->getParameter('admin_email');