nixos: shiboken2 & wxpython broken for 3.12

Change of default python to 3.12 broke freecad & kicad because wxpython & shiboken2 depend on <3.12. To be fixed later™️

machines/universedesktop/programs/cad.nix

@@ -1,8 +1,10 @@
 { lib, config, pkgs, ... }: {
   environment.systemPackages = with pkgs; [
     openscad
-    freecad
-    kicad
+    # https://github.com/NixOS/nixpkgs/pull/326595
+    (freecad.override {python3Packages = pkgs.python311.pkgs;})
+    # https://github.com/NixOS/nixpkgs/pull/325726
+    (kicad.override {python3 = pkgs.python311;})
 
     prusa-slicer
   ];