Remove deprecated call to renderSingleView

Summary: Return an array of renderables instead of rendering things ourselves (which we used to do with `AphrontView->renderSingleView()`.)

Test Plan: View a Releeph branch; gloriously notice no deprecated warnings.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5363