natron: use python312

Shiboken2 is broken on Python 3.13.

pkgs/applications/video/natron/default.nix

···
   extra-cmake-modules,
   glog,
   libXdmcp,
-  python3,
+  python312,
   wayland,
 }:
 
···
     rev = "Natron-v${minorVersion}";
     hash = "sha256-TD7Uge9kKbFxOmOCn+TSQovnKTmFS3uERTu5lmZFHbc=";
   };
+  python3 = python312;
 in
 stdenv.mkDerivation {
   inherit version;