fix: TaskProcessingAPI - unregister provider endpoint

[bigcat88]

Found this when writing a small test for nc_py_api

without this change $taskProcessingProvider->id are always null

$taskProcessingProvider = $this->getExAppTaskProcessingProvider($appId, $name);
if ($taskProcessingProvider !== null) {
    $this->mapper->delete($taskProcessingProvider);
    $this->resetCacheEnabled();
    return $taskProcessingProvider;
}