python3Packages.sat-tmp: Drop auto-added passthru.updateScript

nix-update doesn't handle mercurial sources.

pkgs/development/python-modules/sat-tmp/default.nix

···
   # no pytest tests exist
   doCheck = false;
 
+  # Default-added updateScript doesn't handle Mercurial sources
+  passthru.updateScript = null;
+
   meta = {
     description = "Libervia temporary third party patches";
     longDescription = ''