Remove obsolete, no-op implementations of "willRenderTimeline()"

Summary:
Depends on D19918. Ref T11351. In D19918, I removed all calls to this method. Now, remove all implementations.

All of these implementations just return $timeline, only the three sites in D19918 did anything interesting.

Test Plan: Used grep willRenderTimeline to find callsites, found none.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T11351

Differential Revision: https://secure.phabricator.com/D19919