modules/nixos: remove update-diff

moved to srvos

modules/nixos/common/default.nix

@@ -18,15 +18,6 @@
     inputs.srvos.nixosModules.server
   ];
 
-  srvos.update-diff.enable = false;
-  system.preSwitchChecks.update-diff = ''
-    if [[ -e /run/current-system && -e "''${1-}" ]]; then
-      echo "--- diff to current-system"
-      ${pkgs.nvd}/bin/nvd --nix-bin-dir=${config.nix.package}/bin diff /run/current-system "''${1-}"
-      echo "---"
-    fi
-  '';
-
   # Hard-link duplicated files
   nix.settings.auto-optimise-store = true;
   nix.optimise.automatic = false;