> dev docs direct to `/license.html` which redirects to `/3/license.html`

All docs are redirecting to `/license.html`, this allow it to work also out of docs.python.org.

> 3.9 docs have the same; wouldn’t it be better to have `/3.9/license.html`?

It's maybe a slight better yes (the page should be the same so I don't know if it make real difference), but doing so means a bit of complexity, which I don't think is worth it.

I tried to keep it simple for this fix (the previous state was "links to the current page" which was worse).