Use celerity for document_black.png in PhabricatorStandardPageView

Summary:
The image was incorrectly served on /rsrc without using celerity. This
is no longer routable with recommendations in D9401.

Test Plan: Browse to home page and inspect javascript link for this resource.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10040