Cancel orders for a market using order hashes.

• May be a single order hash or a list of order hashes.

• All orders must belong to the same account.

• If no order hashes are specified, then will cancel all orders for the given market

• All orders being cancelled by request will receive the same time priority.

{
  "orderHashes": [
    "order_hash1",
    "order_hash2"
  ]
}