[cashtab] Ignore eslint false positive for jest import

Summary:
From eslint:

Jest is automatically in scope. Do not import "jest", as Jest doesn't export anything.

However this only stands for test files, jest is not automatically in the scope of other files and this causes a false positive, which can be safely ignored with an eslint single line error ignre comment.

Test Plan:

cd web/cashtab
npm ci
npm test
eslint scripts/test.js

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D12924