Switch to QEmu agent- not yet available

Signed-off-by: Benoit Donneaux <benoit@leastauthority.com>

morph/lib/hardware-vagrant.nix

@@ -15,7 +15,8 @@
   };
 
   config = {
-    #virtualisation.virtualbox.guest.enable = true;
+    # Apparently not yet available in nixpkgs 21.11
+    # virtualisation.qemu.guestAgent.enable = true;
 
     boot.loader.grub.device = "/dev/vda";