Update Jupyter-Dev instructions

[jbkalmbach]

We have gotten a little bit of feedback from people starting to try jupyter-dev in the collaboration. I have gotten some notes on issues that came up and will add to the notes.

[kadrlica]

Adding a note, it appears that the setup script pointed to by lsst-kernel.sh, i.e.
/global/common/cori/contrib/lsst/lsstDM/setupStack-12_1-Run3.1-a.sh
doesn't exist anymore.

[jbkalmbach]

Thanks, I'll find the new location and update this.

[kadrlica]

Here's a version that I put together at the DESC sprint week:
(https://github.com/LSSTDESC/SSim_DC1/blob/master/Notebooks/lsst-kernel.sh