core/api-spec: remove account id from spend_account_unspent_output params
core/api-spec: remove account id from spend_account_unspent_output params

The account_id is not required to find the output.

Closes chain/chainprv#1286.
Reviewers: da39a3ee5e6b4b0d3255bfef95601890afd80709@erykwalder




chain/chain,chain/chain,chain/chain,chain/chain,chain/chain,chain/chain