thinice: Remove draw_polygon() from style class
thinice: Remove draw_polygon() from style class

The hook has been deprecated/removed from GtkStyle.

https://bugzilla.gnome.org/show_bug.cgi?id=626678

Reviewed-by: Benjamin Otte <8a18bc6febee485a228a7d9ada210dc3778cd199@redhat.com>

GNOME/gtk-engines,GNOME/gtk-engines,GNOME/gtk-engines,GNOME/gtk-engines