Remove middleware for checking for maintenance

This is (mostly) a built-in feature in Laravel 5.3

app/Http/Kernel.php

@@ -14,7 +14,6 @@ class Kernel extends HttpKernel
      * @var array
      */
     protected $middleware = [
-        \MisterPhilip\MaintenanceMode\Http\Middleware\CheckForMaintenanceMode::class,
         \Illuminate\Session\Middleware\StartSession::class,
         \Illuminate\View\Middleware\ShareErrorsFromSession::class,
         \App\Http\Middleware\FrameGuard::class,