[Cashtab] Remove qr fallback artifact

Summary:
T2813

Remove Path 245 fallback support from Receive screen. This was introduced when migrating to a new derivation path two years ago and is no longer required.

Test Plan:
npm start
Navigate to receive screen with no unusual dev console errors
Change wallets
Confirm still no errors

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D12687