GWX is a great tool for removing the Windows 10 upgrade notification:


http://ultimateoutsider.com/downloads/


Alternatively, our staff usually will remove/uninstall the KB3035583 Windows Update, refresh the Windows Updates (before rebooting), then hide the update, and finally reboot.  The following page also includes some regedits that they've had to do:


http://www.howtogeek.com/218856/how-do-you-disable-the-get-windows-10-icon-shown-in-the-notification-tray/


Ideally, we recommend using GWX as that is the easiest way to remove all notifications to install/upgrade to Windows 10.