pin jupyterlab to 4.2

[ateucher]

Jupyterlab is showing some strange behaviour in the hub. From Slack:

I've been working on some stuff for a workshop on the hub and I'm having an issue where if I edit a python file, the edits seem to be going to a different place in the file than where they are displayed in the editor. If I re-open the file, they end up with different spacing and on a different line. Anyone seen something like this?