status: Clean up imports

https://bugzilla.gnome.org/show_bug.cgi?id=680426

js/ui/status/network.js

@@ -1,12 +1,9 @@
 // -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
-const ByteArray = imports.byteArray;
 const GLib = imports.gi.GLib;
 const GObject = imports.gi.GObject;
 const Lang = imports.lang;
-const Mainloop = imports.mainloop;
 const NetworkManager = imports.gi.NetworkManager;
 const NMClient = imports.gi.NMClient;
-const Shell = imports.gi.Shell;
 const Signals = imports.signals;
 const St = imports.gi.St;