[Pkg-mpd-maintainers] Bug#967436: gmpc: depends on deprecated GTK 2

[Bastian Germann]

From: "Simon McVittie" <smcv at debian.org>
> - https://github.com/DaveDavenport/gmpc is a fork that has been ported
>    to GTK 3, but is specifically labelled as unmaintained, has never done
>    a release, and hasn't changed since 2020;

Yes, DaveDavenport is the one with gtk3 support. I suppose it is better to have
an unmaintained gtk3 version instead of an unmaintained gtk2 version.