[Cashtab] [p4 normalizeBalance fix] Change function input to nonSlpUtxos

Summary:
T2601

Depends on D11845

Part 4 in a series of diffs to improve calculation of wallet balance from utxo set

Modify the normalizeBalance function to accept nonSlpUtxos as input, instead of its parent object. The function only uses nonSlpUtxos so the parent object is not necessary.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D11846