[Cashtab] [p2 normalizeBalance fix] Remove unused import from cashMethods.test.js

Summary:
T2601

Part 2 in a series of diffs to improve calculation of wallet balance from utxo set

Depends on D11843

Remove unused import from cashMethods.test.js in preparation for adding unit tests for the normalizeBalance function

Test Plan: npm test and confirm no impact

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D11844