Fix runtime fatal error Declaration in Yii2.php

Upgrading `symfony/browser-kit` from `v6.4.0` to `v7.0.0` getting runtime error.

Author: jafaripur

src/Codeception/Lib/Connector/Yii2.php

@@ -480,7 +480,7 @@ protected function mockMailer(array $config)
         return $config;
     }
 
-    public function restart()
+    public function restart(): void
     {
         parent::restart();
         $this->resetApplication();