Updated the docs so chatbots can use the Conduit API

Summary: Previously, the chatbot docs instructed users to get certificates for the conduit API and put the cert in a conduit.cert config key. In order to get the chatbot to work, I needed to instead get an API key and put it in the conduit.token config entry.

Test Plan: Doc fix. Tried the new documented way and it worked.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D16443