remove default callback

services/docstore/test/acceptance/js/helpers/DocstoreClient.js

@@ -61,10 +61,7 @@ module.exports = DocstoreClient = {
   },
 
   peekDoc(project_id, doc_id, qs, callback) {
-    if (callback == null) {
-      callback = function (error, res, body) {}
-    }
-    return request.get(
+    request.get(
       {
         url: `http://localhost:${settings.internal.docstore.port}/project/${project_id}/doc/${doc_id}/peek`,
         json: true,