tests/test-gendoc-fr.t

config: fix fm.data() handling of defaultvalue

This is a follow-up patch to rHG51a2e3102db2. This moves
`fm.data()` out of the if block in `commands.config()`.

Differential Revision: https://phab.mercurial-scm.org/D6720

#require docutils gettext

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