Process the translated data for this field back into a structure that can be saved by the content entity.
array $field_data: The translated data for this field.
\Drupal\Core\Field\FieldItemListInterface $field: The field object.
\Drupal\tmgmt_content\Plugin\tmgmt\Source\ContentEntitySource::doSaveTranslations()
public function setTranslations($field_data, FieldItemListInterface $field);