[e.cash] Remove tagline about Avalanche

Summary:
Some people get confused by this line, and think it's related to AVAX.
Probably better to have the text simpler anyway.

Test Plan: Run it locally, see that it looks good.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: Sintayew4

Differential Revision: https://reviews.bitcoinabc.org/D17161