preprocess_html remove attributes

the implementation removes all predefined attributes like "prefix,lng,ltr etc"
the function toolbar_anti_flicker preprocess_html should change from:

function toolbar_anti_flicker_preprocess_html(&$variables) {
  if (!\Drupal::currentUser()->hasPermission('access toolbar')) {
    return;
  }
  $attributes = array();
  $attributes['class'] = 'toolbar-no-flickering';
  $variables['html_attributes']['class'] = new Attribute($attributes);
}

to:

function toolbar_anti_flicker_preprocess_html(&$variables) {
  if (!\Drupal::currentUser()->hasPermission('access toolbar')) {
    return;
  }
  $variables['html_attributes']->addClass('toolbar-no-flickering');
}