Use PhutilClassMapQuery instead of PhutilSymbolLoader

Summary: Use `PhutilClassMaQuery` instead of `PhutilSymbolLoader`, mostly for consistency. Depends on D13588.

Test Plan: Poked around a bunch of pages.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13589

scripts/setup/manage_remove.php

@@ -14,8 +14,8 @@ EOSYNOPSIS
   );
 $args->parseStandardArguments();
 
-$workflows = id(new PhutilSymbolLoader())
+$workflows = id(new PhutilClassMapQuery())
   ->setAncestorClass('PhabricatorSystemRemoveWorkflow')
-  ->loadObjects();
+  ->execute();
 $workflows[] = new PhutilHelpArgumentWorkflow();
 $args->parseWorkflows($workflows);