spice-gtk: 0.35 -> 0.37

Meson!

Pulseaudio backend has been deprecated upstream
so it has been disabled. Celt has also been disabled
because there's opus.

Other than that optional features have been enabled.

https://gitlab.freedesktop.org/spice/spice-gtk/blob/v0.36/NEWS
https://gitlab.freedesktop.org/spice/spice-gtk/blob/v0.37/NEWS