tzdata/tzcode: leave only latest version

tzdata/tzcode: leave only latest version

I don't see any value in old tzdata/tzcode-native recipes as tzcode is only
used to compile tzdata and compiled tzdata should be compatible with any
version of glibc and it's good to have it latest. So I think we should only
leave latest tzdata version and move that forward whenever someone discovers
that elsie.nci.nih.gov dropped that version. Same for tzcode.

Add comments to unconditionally move that versions forward whenever there is
a new release.

Signed-off-by: Roman I Khimov <khimov@altell.ru>