Remove all stray imports to imports.dbus

Some modules were importing DBus without actually using it.

https://bugzilla.gnome.org/show_bug.cgi?id=648651

js/ui/userMenu.js

@@ -1,7 +1,6 @@
 // -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
 
 const AccountsService = imports.gi.AccountsService;
-const DBus = imports.dbus;
 const Gio = imports.gi.Gio;
 const GLib = imports.gi.GLib;
 const Lang = imports.lang;