tests/test-gendoc-sv.t

run-tests: fix a typo in an attribute name

At least, I assume it's a typo.  Nothing else uses it, but `_tmpbindir` is used.

Differential Revision: https://phab.mercurial-scm.org/D9542

#require docutils gettext

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