Bug#967257: ardour: depends on deprecated GTK 2

[Erich Eickmeyer]

Ardour 8.3 has been released and no longer depends on deprecated GTK2 as 
a modified version is bundled within. https://ardour.org/whatsnew83.html

Considering ardour has been scheduled for autoremoval on 06 March 
(#1061203), I highly recommend getting this updated as soon as possible 
to avoid this removal. Since the library is now bundled, the dependency 
on libgtk2.0-dev can be dropped.

Thanks,
Erich
--
Erich Eickmeyer
Ubuntu MOTU
Project Leader - Ubuntu Studio
Technical Lead - Edubuntu