[Cashtab] [p6 and final of normalizeBalance improvements] Remove double definition of this function in useWallet

Summary:
T2601

Depends on D11847

Remove the normalizeBalance function from useWallet.js, as it is already defined and unit tested in CashMethods.js. Adjust the input to be the needed nonSlpUtxos array and not its parent slpBalancesAndUtxos object

Test Plan: npm start and make sure your wallet has the same balance as before, works normally.

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D11848