Issue #3325772 by andypost, mondrake: Fix wrong property typehinting in SchemaCheckTrait

  /**

   * The config schema wrapper object for the configuration object under test.

   *

   * @var \Drupal\Core\Config\Schema\Element

   */

  protected $schema;

  protected TraversableTypedDataInterface $schema;

  /**

   * The configuration object name under test.

   *

   * @var string

   */

  protected $configName;

  protected string $configName;

  /**

   * Checks the TypedConfigManager has a valid schema for the configuration.