Fix libvirtd group

configuration.nix

@@ -40,7 +40,7 @@
   # Define a user account. Don't forget to set a password with ‘passwd’.
   users.users.thomas = {
     isNormalUser = true;
-    extraGroups = [ "wheel" "video" "networkmanager" "libvirt" ];
+    extraGroups = [ "wheel" "video" "networkmanager" "libvirtd" ];
     shell = pkgs.zsh;
   };