add Depends: gir1.2-spiceclientgtk-3.0

Thanks to @onions-knight for the bug report!

https://forums.whonix.org/t/whonix-desktop-installer-with-calamares-field-report/7350/118

debian/control

@@ -14,7 +14,7 @@ Standards-Version: 4.3.0
 Package: whonix-libvirt
 Architecture: all
 Depends: qemu-kvm, libvirt-daemon-system, libvirt-clients, virt-manager,
- dnsmasq-base, helper-scripts, ${misc:Depends}
+ gir1.2-spiceclientgtk-3.0, dnsmasq-base, helper-scripts, ${misc:Depends}
 Description: Whonix Libvirt XML Files for KVM and QEMU
  Libvirt XML files for Whonix-Gateway, Whonix-Workstation,
  Whonix-Custom-Workstation and Whonix's internal network.