Fix UpdateSettingsForm dependency injection

The UpdateSettingsForm class doesn't implement the create() method as per the documentation

https://api.drupal.org/api/drupal/core%21modules%21update%21src%21Update...

  public static function create(ContainerInterface $container) {
    $instance = parent::create($container);
    $instance->emailValidator = $container
      ->get('email.validator');
    return $instance;
  }

The form class should have a __construct method and then provide all injected dependencies in the create method.