Inaccurate guessFee calculation on Send many.

[talshalti]

My-Wallet-V3/src/transaction.js

Line 188 in c9c3543

accFee = Transaction.guessFee(ii + 1, 2, fee);

Using sendmany and fee_per_byte results in lower fee per byte than stated, since the calculation is based on assuming there's only 2 output addresses.