Entity type annotation label_callback is deprecated

The ability to define a label callback in the entity type definition has been deprecated.

Entity types that have a dynamic label can instead override the label method.

Before

 *   label_callback = "user_format_name",

function user_format_name(AccountInterface $account) {
  return $account->getDisplayName();
}

After

/**
   * {@inheritdoc}
   */
  public function label() {
    return $this->getDisplayName();
  }