BUG: follow-up on jupyterbook.org JB2

[bsipocz]

Describe the bug

The RTD build cannot find the intersphinx for jupyterbook.org. Besides that we may need to sweep the links to make sure we link everywhere to JB1 explicitly.

Reproduce the bug

RTD CI is failing, but you should see the intersphinx error when building the docs locally, too.

List your environment

No response