[Cashtab] Deprecate cashaddrjs for ecashaddrjs

Summary:
cashaddrjs has already been functionally replaced with ecashaddrjs throughout the app. This diff removes one missed mention of cashaddrjs from a unit test and also removes the npm package.

Note that ecashaddrjs is an exact fork of cashaddrjs except it also supports ecash: and etoken: as valid prefixes

T1738

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9895