Instructions for persistent `pip install` don't work

[troyraen]

Our instructions at https://docs.fornax.sciencecloud.nasa.gov/compute-environments#update-an-existing-environment say that the to install a package that persists through server restarts we should add the --user option to the command. That option raises an error for me and the software doesn't install at all.

(python3) jovyan@jupyter-raen:~$ pip install jupyterlab-a11y-checker --user
ERROR: Can not perform a '--user' install. User site-packages are not visible in this virtualenv.
(python3) jovyan@jupyter-raen:~$ uv pip install jupyterlab-a11y-checker --user
error: pip's `--user` is unsupported (use a virtual environment instead)

Need to find the right instructions and update the docs.

[troyraen]

Here are the related uv docs: https://docs.astral.sh/uv/pip/compatibility/#-user-and-the-user-install-scheme