Upgrade to Laravel 9 (#4413)

Co-authored-by: DaneEveritt <dane@daneeveritt.com>

tests/CreatesApplication.php

@@ -2,16 +2,15 @@
 
 namespace Pterodactyl\Tests;
 
+use Illuminate\Foundation\Application;
 use Illuminate\Contracts\Console\Kernel;
 
 trait CreatesApplication
 {
     /**
      * Creates the application.
-     *
-     * @return \Illuminate\Foundation\Application
      */
-    public function createApplication()
+    public function createApplication(): Application
     {
         $app = require __DIR__ . '/../bootstrap/app.php';