A typical deprecation that you can find in your custom code is:

Function entity_delete_multiple not found.

How to fix this

Change your code from

$results = \Drupal::entityQuery('node')
   ->condition('type', 'article')
   ->execute();

if ($hasResults) {
 entity_delete_multiple('node', $results);
}

to

if ($hasResults) {
  $storage_handler = \Drupal::entityTypeManager()->getStorage('node');
  $storage_handler->delete($results);
}