Convert phutil_render_tag(X, Y) to phutil_tag

Summary:
Created with spatch:

- phutil_render_tag
+ phutil_tag
  (X, Y)

(and null manually)

Test Plan: Loaded homepage

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4500