Links in footer section "Probabilistic Numerics" are dead

[simeoncarstens]

When I visit https://probnum.readthedocs.io, on the bottom there's a range of interesting-looking links, e.g., "In a nutshell". Unfortunately they are all dead and lead to a readthedocs.io error page.

[JonathanWenger]

Thanks for pointing out the bug! This happened when in #586 the probabilistic numerics section was removed and moved to a separate website https://www.probabilistic-numerics.org/.

[mmahsereci]

Hey @simeoncarstens , good to see you here! :)

@JonathanWenger we could either remove all those links as the probabilistic numerics web page is now separate from the ProbNum page, or simply fix the links. Any preference? I don't really mind.