Use of deprecated entity_delete_multiple on user delete

Problem/Motivation

Deleting a user account calls _quiz_delete_users_results which uses entity_delete_multiple() function. This function has been removed from D9.

Steps to reproduce

Behavior is a non-fatal error upon user account deletion

Proposed resolution

Replace entity_delete_multiple() with process shown here https://api.drupal.org/api/drupal/core%21includes%21entity.inc/function/...

$controller = \Drupal::entityTypeManager()->getStorage('quiz_result');
$entities = $controller->loadMultiple($result_ids);
$controller->delete($entities);