[ecash-herald] Tighter token send descriptions

Summary: The address info on token send txs is not really useful and can be found by investigating the txid. Remove this info so token send msgs simply provide amount and token ticker.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14435