ContactAccessControlHandler edit operation does not exist.

In Drupal\content_entity_example\ContactAccessControlHandler you have the following method:

 /**
   * {@inheritdoc}
   *
   * Link the activities to the permissions. checkAccess is called with the
   * $operation as defined in the routing.yml file.
   */
  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
    switch ($operation) {
      case 'view':
        return AccessResult::allowedIfHasPermission($account, 'view contact entity');

      case 'edit':
        return AccessResult::allowedIfHasPermission($account, 'edit contact entity');

      case 'delete':
        return AccessResult::allowedIfHasPermission($account, 'delete contact entity');
    }
    return AccessResult::allowed();
  }

the "edit" operation does not exist, this should be changed to update.

Patch attached.