Bump number of visible Maniphest tags to 4 (from 2)

Summary: Ref T3574. Since this list just clips in a totally reasonable way on mobile and we got another user request for it, let's bump this to 4 for now and we can refine mobile later.

Test Plan: Looked at list on desktop; saw 4 tags before truncation. Looked at list on mobile, saw reasonable clipping behavior which didn't mar usability.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T3574

Differential Revision: https://secure.phabricator.com/D8213