Python return_unconverged docs off

[peekxc]

For the Python interface, return_unconverged and raise_for_unconverged are options documented in the docstrings, but not on the online docs.

It would be nice to get a better idea of how these are related to the eigenvalues.

My guess is that primme just runs to maxiter / whenever convtest succeeds, and then internally calls something like eigh_tridiagonal on whatever Ritz values have been obtained in the iteration. Is that correct?