python3Packages.dicttoxml2: migrate to pyproject

pkgs/development/python-modules/dicttoxml2/default.nix

@@ -2,18 +2,21 @@
   lib,
   buildPythonPackage,
   fetchPypi,
+  setuptools,
 }:
 
 buildPythonPackage rec {
   pname = "dicttoxml2";
   version = "2.1.0";
-  format = "setuptools";
+  pyproject = true;
 
   src = fetchPypi {
     inherit pname version;
     hash = "sha256-Z8tynzN911KAjAIbcMjfijT4S54RGl26o34ADur01GI=";
   };
 
+  build-system = [ setuptools ];
+
   # Module has no tests
   doCheck = false;