kmscon service: disable systemd-vconsole-setup

cc #22470.

nixos/modules/services/ttys/kmscon.nix

···
           ln -s ${config.systemd.units."kmsconvt@.service".unit}/kmsconvt@.service $out/autovt@.service
         '';
 
-    systemd.services.systemd-vconsole-setup.restartIfChanged = false;
+    systemd.services.systemd-vconsole-setup.enable = false;
 
     services.kmscon.extraConfig = mkIf cfg.hwRender ''
       drm