[website] add a note to remote CashFusion tutorial for Electrum ABC 5.1.6

Summary:
load_wallet is now a regular RPC command.

See https://github.com/Bitcoin-ABC/ElectrumABC/pull/244/commits/39a0ff0b5616fc87a8e02918bfbb9bc5c749de36

Test Plan: Run the website locally and browse http://127.0.0.1:8080/2022-07-01-running-cashfusion-remotely/

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12403