Removes an (unprinted) consignment item and returns any labels to the pool.
ConsignmentItemID - The itemID of the consignment item (see List Consignments)
A data structure like so:
{ 'result': { 'Success': true, 'ConsignmentItemID': '1620683' } }
https://nz.api.fastway.org/latest/fastlabel/removeconsignmentitem?ConsignmentItemID=1&api_key=YOUR_API_KEY