Update jupyter environment

A few haskell packages can't be built,
so some notebooks will not compile.
Still, we're in a better place than before.

Further, I had to remove haskell-flake-utils,
it seems not to be supported sufficiently.
This dropped cabal-docspec support.

I also had to remove the nixpkgs follow input,
otherwise there would be an infinite loop:
(tweag/jupyenv#525)