Allow TrueTypeOS2Table::from_face on all OSes
Allow TrueTypeOS2Table::from_face on all OSes

freetype-sys FT_Get_Sfnt_Table() has been updated to be available on all
OSes therefore the TrueTypeOS2Table::from_face OS whitelist can be
removed as well.

PistonDevelopers/freetype-rs,bvssvni/freetype-rs