nbstripout: Don't propagate ipython (#230164)

If you have a devShell with `python311` and `nbstripout` in `buildInputs`, running `python --version` will output 3.10 as of today, because `nbstripout` is propagating python through ipython.

Changed files
-1
pkgs
applications
version-management
nbstripout
-1
pkgs/applications/version-management/nbstripout/default.nix
···
'';
propagatedBuildInputs = with python3.pkgs; [
-
ipython
nbformat
];