views_ajax_form_wrapper() replaced by \Drupal\views_ui\Form/Ajax/ViewsFormBase::ajaxFormWrapper()

views_ajax_form_wrapper() is moved to a protected method in the \Drupal\views_ui\Form\ViewsFormBase base class.

Before

<?php
$response = views_ajax_form_wrapper($form_class, $form_state);
?>

After

<?php
$response = $this->ajaxFormWrapper($form_class, $form_state);
?>

So, to use this function, your form will need to extend this base class.