Reset the auto generated path of an entity and regenerate.

example.post_update.php

<?php

use Drupal\pathauto\PathautoState;

/**
 * Regenerate FAQ category URL's.
 */
function example_post_update_regenerate_node_urls(&$sandbox) {
  return example_regenerate_urls($sandbox, 'taxonomy_term', ['faq_category']);
}

/**
 * Generate URL for an entity type and a list of bundles.
 */
function example_regenerate_urls(&$sandbox, $entity_type_id, $bundles) {
  $chunk_size = 10;

  /** @var \Drupal\pathauto\PathautoGenerator $pathautoGenerator */
  $pathautoGenerator = \Drupal::service('pathauto.generator');
  $entity_type_manager = \Drupal::entityTypeManager();
  $entity_type = $entity_type_manager->getDefinition($entity_type_id);
  $storage_manager = $entity_type_manager->getStorage($entity_type_id);
  $id_field = $entity_type->getKey('id');

  if (empty($sandbox['entity_chunks'])) {
    $select = \Drupal::database()->select($entity_type->getBaseTable(), 'base_table');
    $select->addField('base_table', $id_field, $id_field . '_1');
    $select->addField('base_table', $id_field);
    $select->condition('base_table.' . $entity_type->getKey('bundle'), $bundles, 'IN');
    $ids = $select->execute()->fetchAllKeyed();

    $sandbox['total'] = count($ids);
    $sandbox['entity_chunks'] = array_chunk($ids, $chunk_size);
  }

  $ids = array_pop($sandbox['entity_chunks']);
  foreach ($storage_manager->loadMultiple($ids) as $entity) {
    $entity->path->pathauto = PathautoState::CREATE;
    $pathautoGenerator->updateEntityAlias($entity, 'bulkupdate', [
      'message' => FALSE,
      'force' => TRUE,
    ]);
    \Drupal::keyValue('pathauto_state.' . $entity->getEntityTypeId())
      ->set(PathautoState::getPathautoStateKey($entity->id()), PathautoState::CREATE);
  }

  $sandbox['#finished'] = empty($sandbox['entity_chunks']) ? 1 :
    ($sandbox['total'] - (count($sandbox['entity_chunks']) * $chunk_size)) /
    $sandbox['total'];
}