tests/test-gendoc-zh_CN.t

context: move contents of committablectx.markcommitted() to workingctx

Same reasoning as previous commits: this function updates the
dirstate. By not updating the dirstate here, we also fix the
close-head test.

Differential Revision: https://phab.mercurial-scm.org/D6365

#require docutils gettext

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