This fixes an issue when, if an external font path was modified in the
Windows key, it was then not considered as external anymore, but still
present in the external key, and then dropped from both on update.

This now forcefully updates the font path in both keys if needed.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>