package/lua-utf8: bump to version 0.1.2

switch of rocks maintainer
from https://luarocks.org/modules/dannote/utf8
to https://luarocks.org/modules/xavier-wang/luautf8

the upstream author stays http://github.com/starwing/luautf8



now, the version scheme is aligned on the upstream one,
and the version 0.1.2 was released on 06 Apr 2020.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>