tests/test-gendoc-zh_TW.t

color: handle 'ui.plain()' directly in mode setup

If 'ui.plain()' is set we should not colorize. We move that logic into the
function that determine and setup the color mode. As all other code respect
the resulting mode this will be equivalent.

#require docutils gettext

  $ $TESTDIR/check-gendoc zh_TW
  checking for parse errors