Use form title (if present) for delete modal

For the add/edit modal we have the following logic for the modal title:

    $page_title = isset($form['#title']) ? $form['#title'] : $this->t('Delete @label', ['@label' => $entity->label()]);
    $response->addCommand(new OpenModalDialogCommand($page_title, $form, ['width' => '800px']));

For the delete modal, however, there's this logic:

$response->addCommand(new OpenModalDialogCommand(t('Delete @label', ['@label' => $entity->label()]), $form, ['width' => '800px']));

Let's align the delete modal title to that of the add/edit modal.