ui: Wait for i18n setup before rendering hotkeys help.

Much like 038a2c769, but for the three tabs at the top of the
`?` help overlay for keyboard shortcuts.

static/js/ui_init.js

@@ -269,6 +269,7 @@ $(function () {
     drafts.initialize();
     sent_messages.initialize();
     compose.initialize();
+    ui.initialize();
 });