Reapply "update-diff: nvd -> dix"

https://github.com/faukah/dix?tab=readme-ov-file#usage-in-ci

This reverts commit 7f3bc43.

Author: zowoq

shared/common/update-diff.nix

@@ -12,8 +12,8 @@
     };
     command = lib.mkOption {
       type = lib.types.singleLineStr;
-      default = "${pkgs.nvd}/bin/nvd --nix-bin-dir=${config.nix.package}/bin diff";
-      defaultText = lib.literalExpression ''"''${pkgs.nvd}/bin/nvd --nix-bin-dir=''${config.nix.package}/bin diff"'';
+      default = "${lib.getExe pkgs.dix} --force-correctness";
+      defaultText = lib.literalExpression ''"''${lib.getExe pkgs.dix} --force-correctness"'';
       description = "diff command";
     };
     text = lib.mkOption {