Remove batch finishCallback

Problem/Motivation

In EntityTypeBehaviorStorageBatchHandler::generateBatch there is following returned:

return [
    'title' => $this->t('Starting behavior storage field update'),
    'operations' => $operations,
    'finished' => [$this, 'finishCallback'],
];

The given array for 'finished' causes following Error (with Drupal ^11.3), when saving e.g. a content type like the one under admin/structure/types/manage/page:
Error: Object of class Drupal\entity_type_behaviors\Batch\EntityTypeBehaviorStorageBatchHandler could not be converted to string in implode() (line 69 of /var/www/html/web/core/lib/Drupal/Core/Utility/CallableResolver.php).

This part, anyways, is strange, as the function 'finishCallback' doesn't exist.

Proposed resolution

As 'finishCallback' doesn't exist, i assume, it's not needed. Therefore just remove it, until there is an idea/concept for the need of this callback.