Reduce application search engine results list for Dashboards

Summary: Ref T10390. Simplifies dropdown by rolling out canUseInPanel in useless panels

Test Plan: Add a query panel, see less options.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T10390

Differential Revision: https://secure.phabricator.com/D17341

src/applications/files/query/PhabricatorFileSearchEngine.php

@@ -11,6 +11,10 @@ final class PhabricatorFileSearchEngine
     return 'PhabricatorFilesApplication';
   }
 
+  public function canUseInPanelContext() {
+    return false;
+  }
+
   public function newQuery() {
     return new PhabricatorFileQuery();
   }