fix descriptor for khttp

[devcrocod]

Link to source is broken
Actually, I couldn’t find the current repository for this library
Also, I couldn’t follow their quickstart as the necessary import was missing, and I got an exception

I think it should be removed since it’s unsafe without the source code

kotlin-jupyter-libraries/khttp.json

Line 7 in c132ba8

"link": "https://github.com/jkcclemens/khttp",