Cross reference to neuron documentation is failing on latest

`nrn-patch` is using neuron python documentation to refer to its object classes. With recent changes in neuron documentation, the [page](https://nrn.readthedocs.io/en/8.2.7/python/programming/python.html) containing these refs were removed.

See [related issue](https://github.com/neuronsimulator/nrn/issues/3578) on neuron.