Radon Stan case study linking to ipynb instead of html

[avehtari]

In case-studies.qmd other case studies link to a html, but on line 914 radon case study links to ipynb which doesn't render to something useful in a web browser

stan-dev.github.io/learn-stan/case-studies.qmd

Line 914 in e37e400

[View](../learn-stan/case-studies/radon.ipynb){target="_blank"}(HTML)

I don't know how to fix this, so making an issue. Maybe @mitzimorris knows what to do?

[mitzimorris]

I think the fix is to clone this repo: https://github.com/fonnesbeck/stan_workshop_2016, render the notebook "MultilevelModeling.ipynb" to html and add the rendered HTML to directory learn-stan/case-studies. I will try this over the weekend.