Use __CLASS__ instead of hard-coding class names

Summary: Use `__CLASS__` instead of hard-coding class names. Depends on D12605.

Test Plan: Eyeball it.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: hach-que, Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12806

src/applications/help/application/PhabricatorHelpApplication.php

@@ -43,7 +43,7 @@ final class PhabricatorHelpApplication extends PhabricatorApplication {
       array(
         'bubbleID' => $help_id,
         'dropdownID' => 'phabricator-help-menu',
-        'applicationClass' => 'PhabricatorHelpApplication',
+        'applicationClass' => __CLASS__,
         'local' => true,
         'desktop' => true,
         'right' => true,