Add missing shim, fix typo

js/react/util/index.ts

@@ -1,5 +1,5 @@
 // Helper components used in the styleguide, exposed at 'util' in the global scope via the
-//   context option in reaat-styleguidist.
+//   context option in react-styleguidist.
 
 export { MessageParents } from './MessageParents';
 export { BackboneWrapper } from './BackboneWrapper';

test/legacy_bridge.js

@@ -13,7 +13,9 @@ window.Signal = {};
 window.Signal.Backup = {};
 window.Signal.Crypto = {};
 window.Signal.Logs = {};
-window.Signal.Migrations = {};
+window.Signal.Migrations = {
+  getPlaceholderMigrations: () => {},
+};
 
 window.Signal.React = window.Signal.React = {};