Openquad currently not compatible with python 3.13

[ablech]

The compatibility problem arises from a second-order dependence on Numba, which is not yet compatible with the latest python version. This probably originates in our use of the quaternionic package to provide the representation of SO(3) in terms of quaternions.

Although Numba will probably get updated soonish, this problem is likely to occur again with every new python release. Hence it is probably best to drop quaternion support and remove the dependency on quaternionic.