ocamlPackages.ppx_deriving_cmdliner: use Dune 3

pkgs/development/ocaml-modules/ppx_deriving_cmdliner/default.nix

···
   version = "0.6.1";
 
   minimalOCamlVersion = "4.11";
+  duneVersion = "3";
 
   src = fetchFromGitHub {
     owner = "hammerlab";