R1:1567f07e3cc1

Fix some broken links in the cluster documentation

Summary:
Looks like some copy pasta snuck in. Also fixes a missed
parenthesis.

Test Plan: Eyeball it.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15920