Fix PHP 8.4 deprecation warning

Author: eusonlito

src/Generator.php

@@ -42,15 +42,15 @@ class Generator
     /**
      * @param \Illuminate\Config\Repository $config
      * @param \Illuminate\View\Factory $view
-     * @param OutputInterface $output
+     * @param ?OutputInterface $output
      * @param string $helpers
      */
     public function __construct(
         /*ConfigRepository */
         $config,
         /* Illuminate\View\Factory */
         $view,
-        OutputInterface $output = null,
+        ?OutputInterface $output = null,
         $helpers = ''
     ) {
         $this->config = $config;