Fix construction of "View Tasks" URI from user profiles

Summary: Fixes T4995. This uses commas so it shouldn't have `[]`. I think I just derped this a while ago.

Test Plan: fiddled

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T4995

Differential Revision: https://secure.phabricator.com/D9009