tests/test-gendoc-zh_CN.t

rcutil: don't check if defaultrc/ is a directory -- we know it is

`mercurial/defaultrc/` is a directory both in the Mercurial repo and
once installed on a target platform. The directory was created in
c4ce077588d0 (config: introduce "built-in" default configuration
settings in default.d, 2014-09-04). That commit has some more
information, but it still doesn't seem to say that `defaultrc/` (then
called `default.d/`) could be a file. Perhaps the check was there to
allow you to run the same code on an older install/repo?

Differential Revision: https://phab.mercurial-scm.org/D7624

#require docutils gettext

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