Encourage users to work with JupyterLab within a Codespace

[iaindillingham]

The "How to use the OpenSAFELY command-line interface" page contains a section on JupyterLab. Whilst we don't intend to deprecate opensafely jupyter, we should encourage users to work with JupyterLab within a Codespace. Doing so would minimise version mismatches, as opensafely jupyter points to python:latest and hence to python:v1; elsewhere, we have been encouraging users to work with python:v2.

During today's Team REX standup, we discussed removing this section from this page. That's one solution. There will be others! The problem is a user encountering a version mismatch: running code on python:v1 that they intended to run on python:v2 or vice versa. Or, indeed, on jupyter (#1568). Importantly, the user may not know that they encountered a version mismatch.