Set the state of a transfer *sent* to a payee.

def set_offchain_reveal_state(
        transfers_pair: List[MediationPairState],
        payee_address: Address,
) -> None:
    """ Set the state of a transfer *sent* to a payee. """
    for pair in transfers_pair:
        if pair.payee_address == payee_address:
            pair.payee_state = 'payee_secret_revealed'