Remove defunct "download" route in Files pointing to nonexistent controller

Summary:
Depends on D19154. Ref T13094. This controller was removed at some point and this route no longer works.

I plan to add a new `download/` route to let us tighten the `form-action` Content Security Policy.

Test Plan: Grepped for the route and controller, no hits.

Maniphest Tasks: T13094

Differential Revision: https://secure.phabricator.com/D19155

src/applications/files/application/PhabricatorFilesApplication.php

@@ -86,7 +86,6 @@ final class PhabricatorFilesApplication extends PhabricatorApplication {
           'PhabricatorFileTransformListController',
         'uploaddialog/(?P<single>single/)?'
           => 'PhabricatorFileUploadDialogController',
-        'download/(?P<phid>[^/]+)/' => 'PhabricatorFileDialogController',
         'iconset/(?P<key>[^/]+)/' => array(
           'select/' => 'PhabricatorFileIconSetSelectController',
         ),