[proaudio] drobilla: wrong dependency >=webkit-gtk-1.4.0, should be webkit-gtk:2

[Zlobin Nikita]

Currently there are two webkit-gtk 
slots with latest 3. Minimal version, 
searched by build system, is from 2nd 
slot, while ebuild dependency 
(>=webkit-gtk-1.4.0) is satified by 
3rd and even higher as well.