removed --onion feature from update-torbrowser and its man page because torproject took its .onion domain permanently offline (https://trac.torproject.org/projects/tor/ticket/11567) thanks got z (https://www.whonix.org/forum/index.php?action=profile;u=94) for the report (https://www.whonix.org/forum/index.php/topic,277.msg1827.html#msg1827)