Restore missing behavior for Differential keyboard navigation

Summary: Fixes T12086. This got dropped by accident while cleaning up haunting.

Test Plan: Loaed a revision, hit "?", hit n/j/p/etc

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12086

Differential Revision: https://secure.phabricator.com/D17166

src/applications/differential/controller/DifferentialRevisionViewController.php

@@ -464,6 +464,12 @@ final class DifferentialRevisionViewController extends DifferentialController {
 
     Javelin::initBehavior('differential-user-select');
 
+    Javelin::initBehavior(
+      'differential-keyboard-navigation',
+      array(
+        'haunt' => null,
+      ));
+
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setSubheader($subheader)