fix documentation of taxonomy_get_vocabularies()

/**
 * Return an array of all vocabulary objects.
 *
 * @param $type
 *   If set, return only those vocabularies associated with this node type.
 */
function taxonomy_get_vocabularies() {
  return taxonomy_vocabulary_load_multiple(FALSE, array());
}

- there is no $type input parameter
- the @return doc is missing.