Fixed instructions for arc certificate installation

Summary: Yura tried following these instructions and was navigated to the wrong token page. Rather than putting the correct link, the instructions provided by arc install-certificate should be followed instead.

Test Plan: Tested on my local machine.

Reviewers: deadalnix, O1 Bitcoin ABC, #bitcoin_abc, Mengerian

Reviewed By: deadalnix, O1 Bitcoin ABC, #bitcoin_abc, Mengerian

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D800