Cancel a transaction request that has not yet been fully signed or delivered. The only supported state transition is to "canceled". For transaction request full, the request must be in "pendingApproval" or "pendingDelivery" state. For transaction request lite, the request must be in "pendingApproval", "pendingUserCommitment", "pendingUserGShare", "pendingUserRShare", or "pendingUserSignature" state.