Issue #3141917 by Project Update Bot: Automated Drupal Rector fixes

<?php

use Drupal\toastr\Form\ToastrSettingsForm;

/**

 * Implements hook_page_attachments().

 */

    // Get toastr configs.

    $config = \Drupal::config('toastr.settings');

    // Get default settings.

    $default_settings = \Drupal\toastr\Form\ToastrSettingsForm::defaultSettings();

    $default_settings = ToastrSettingsForm::defaultSettings();

    $keys = array_keys($default_settings);

    foreach ($keys as $key) {

      $settings[$key] = is_null($config->get($key)) ? $default_settings[$key] : $config->get($key);