tests/test-gendoc-zh_TW.t

persistent-nodemap: use the intended uuid size

I overlooked this in the initial implementation. The format already supporting
any uuid size so, nothing horrible should happens.

Differential Revision: https://phab.mercurial-scm.org/D10754

#require docutils gettext

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