Fix "legalpad documents" typeahead dataousource

Summary: This slipped through the datasource modernization stuff.

Test Plan: Used search UI.

Reviewers: rush898, btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D10196

src/applications/legalpad/query/LegalpadDocumentSignatureSearchEngine.php

@@ -87,7 +87,7 @@ final class LegalpadDocumentSignatureSearchEngine
       $form
         ->appendChild(
           id(new AphrontFormTokenizerControl())
-            ->setDatasource('/typeahead/common/legalpaddocuments/')
+            ->setDatasource(new LegalpadDocumentDatasource())
             ->setName('documents')
             ->setLabel(pht('Documents'))
             ->setValue(array_select_keys($handles, $document_phids)));