Es sollte nachher so aussehen.
/**
* {@inheritdoc}
*/
public static function getSubscribedEvents()
{
return [
// 'Shopware_Modules_Order_SaveOrder_FilterAttributes' => 'onFilterOrderAttributes',
// 'Shopware\Models\Order\Order::postUpdate' => 'syncCarrier',
// 'Shopware\Models\Order\Order::postPersist' => 'syncCarrier',
];
}