Work around lack of app.update.enabled pref in Firefox 63+
Firefox 63 removes the app.update.enabled pref that we used to prevent the meek and Moat profiles from downloading their own updates (#14203 (moved)). https://bugzilla.mozilla.org/show_bug.cgi?id=1420514
As far as I can tell, there isn't a replacement for the pref. The attached patch works around it by setting other prefs:
user_pref("app.update.interval", 999999999); // don't check for updates user_pref("app.update.auto", false); // if downloaded, don't automatically install user_pref("app.update.doorhanger", false); // don't show an update notice in the UI
I noticed this while testing with a newer Firefox in #28168 (moved). I tested setting these prefs in a Tor Browser 8.0.6, and they didn't have any harmful effect.