[Cashtab] [deprecate etoken addresses p4] Add temp info blurb to Receive

Summary:
T2802

Depends on D12680

Add an info blurb to Receive screen explaining lack of switch. A reminder has been set to remove this in 3 weeks.

Test Plan:
npm start
Navigate to Receive screen
Confirm message is legible, free of typos, makes sense
Test at 320px width for responsiveness

Reviewers: #bitcoin_abc, kieran709

Reviewed By: #bitcoin_abc, kieran709

Differential Revision: https://reviews.bitcoinabc.org/D12681