[tz] Non-valid timezones, is there a rule to remove them?

Howdy! Looking at the zone.tab file I can see a few timezones that, although valid in the past, they are not valid anymore. I can pick as example, reported on the GNOME Bugzilla[0], Asia/Novosibirsk, that used to be UTC+7, but nowadays is considered the same one than Asia/Almaty, which one is UTC+6. How is the rule about keep or remove these not-used-anymore timezones? Would you guys accept a patch removing the not-used-anymore ones? What kind of information should I provide/get to be sure that one timezone could be removed? Thanks is advance and Best Regards. [0]: https://bugzilla.gnome.org/show_bug.cgi?id=722419 -- Fabiano Fidêncio