[website] Update Electrum ABC recommended version in CashFusion blog post

Summary: Recommend most recent version, and remove examples for pre-5.1.6

Test Plan:
tested commands, they seem to work.
Ran the site locally and read it through.

Reviewers: PiRK, #bitcoin_abc

Reviewed By: PiRK, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12845