Better docs on Issue 14671

[nick-youngblut]

While #14671 is considered closed, all of my colleagues and I have independently run into this issue. While #14671 does provide a solution, searching through all of the >10k open/closed issues in this repo is asking a lot, in order to come upon #14671. One of my colleagues stopped using vscode-jupyter because he couldn't figure out the tornado.web.HTTPError: HTTP 403: Forbidden errors that he was getting. I'm glad I found #14671 before giving up on vscode-jupyter.

It would be helpful to add some docs (maybe here) with info on what to do in the situation described by #14671.