remove property

app/Providers/RouteServiceProvider.php

@@ -19,15 +19,6 @@ class RouteServiceProvider extends ServiceProvider
      */
     public const HOME = '/home';
 
-    /**
-     * If specified, this namespace is automatically applied to your controller routes.
-     *
-     * In addition, it is set as the URL generator's root namespace.
-     *
-     * @var string
-     */
-    protected $namespace = null;
-
     /**
      * Define your route model bindings, pattern filters, etc.
      *