tests/test-gendoc-zh_TW.t

store: refactor space delimited list to proper data structure

There is no good reason why are having a space delimited list and then using
`.split()` to get the actual list. Let's convert this into a proper collection.

Differential Revision: https://phab.mercurial-scm.org/D8908

#require docutils gettext

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