[website] update remote CashFusion tutorial about installing tor

Summary:
Tor must now be installed before running fusion.

This is not self-explanatory from the lack of error message when a user tries to start CashFusion without tor:

$ electrum daemon enable_autofuse
Enabling tor for Cash Fusion.
Adding wallet /home/pablo/.electrum-abc/wallets/default_wallet to Cash Fusion.

Test Plan: make run and preview

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14986