nixosTests.plasma5: fix test by enabling sound

Same issue as f59b4cb8d5

nixos/tests/plasma5.nix

@@ -30,6 +30,7 @@ import ./make-test.nix ({ pkgs, ...} :
       enable = true;
       user = "alice";
     };
+    hardware.pulseaudio.enable = true; # needed for the factl test, /dev/snd/* exists without them but udev doesn't care then
     virtualisation.memorySize = 1024;
     environment.systemPackages = [ sddm_theme ];
   };