Fix ambiguous column name in UpdateShipmentStateForCanceledOrders

Fixes ambiguous column error:

`Mysql2::Error: Column 'state' in field list is ambiguous: UPDATE `spree_shipments` INNER JOIN `spree_orders` ON `spree_orders`.`id` = `spree_shipments`.`order_id` SET `state` = 'canceled' WHERE (spree_orders.state = 'canceled')`