Update `notebook` and `xeus-python`

[jtpio]

Update to the following dependencies:

• notebook==7.0.3
• xeus-python=0.15.9
• xwidgets=0.28.0
• xeus-cling=0.15.3

Motivated by the discussion in https://github.com/jupyter-xeus/xeus-python/issues/592

[github-actions[bot]]

:point_left: Launch a Binder on branch jtpio/jupyterlab-demo/update-deps

[jtpio]

Looks tricky to get all xeus / xwidgets dependencies to work together with this update.

[jtpio]

cc @martinRenou @SylvainCorlay @JohanMabille if you know which combination of dependencies could work here