Revert "Don't use the deprecated pango_ft2_font_get_face"

This reverts commit 2dc0c3db.

This doesn't make sense.  It ends up in infinite recursion because
pangofc is calling lock_face on pangoft2, which would recursively
call it on pangofc...

Was causing hang at startup of Inkscape.

If the deprecated warnings are an issue, they need to be dealt with
in some other way.