Drop Drupal 8 support

Closes #3286426

src/Controller/CasMockServerController.php

@@ -97,7 +97,7 @@ class CasMockServerController extends ControllerBase {
       throw new NotFoundHttpException();
     }
 
-    return Response::create($this->getContent($user_data), 200);
+    return new Response($this->getContent($user_data), 200);
   }
 
   /**
@@ -140,7 +140,7 @@ class CasMockServerController extends ControllerBase {
     // responding with a different XML structure. Allow third-party modules to
     // alter the XML document object model (DOM).
     $response_alter_event = new CasMockServerResponseAlterEvent($dom, $username, $user_data);
-    $this->eventDispatcher->dispatch(CasMockServerEvents::RESPONSE_ALTER, $response_alter_event);
+    $this->eventDispatcher->dispatch($response_alter_event, CasMockServerEvents::RESPONSE_ALTER);
 
     return $response_alter_event->getDom()->saveXML();
   }