GrowlTunes 2.0 was a complete rewrite, and during the rewrite that
feature most likely got overlooked. GrowlTunes 2.0+ has no
applescript capability presently, and I don't believe there is any way
to use UI scripting on the menu item. Whether it will return or not I
cannot say right now, although we do have a ticket open for a key
binding to re-show the current track.
http://code.google.com/p/growl/issues/detail?id=471
And possibly that would cover what you need without having to re-add
the applescript command. If you need it for some thing more than just
a keybinding, please tell us your use case.