Drop obsolete gconf override

mythbuntu-default-settings 1.13 in Ubuntu 16.10 includes this gconf override:

/apps/update-notifier/auto_launch false

But update-notifier doesn't use gconf any more.

I'm attaching a completely untested bzr commit that disables notifications.

I'm guessing that this doesn't actually stop update-manager from notifying you of updates. You might want to look into the 'regular-auto-launch-interval' key. If you're doing this kind of thing, I think you should look into enabling unattended upgrades (at least security) by default too.