Update requirements to fix Py3.8 build

[VHellendoorn]

The previous version constraints only successfully built PLUR in a Python 3.9 environment. The below refines some of these versions to work with Python 3.8, and in particular, to be compatible with a Tensorflow 2.8.0-GPU Docker image, which ships with that version of Python by default. I expect that these changes will fix setup bugs in other environments too, and plan to push the corresponding docker image and/or Dockerfile soon to simplify the setup process.

This mostly required freezing a higher version of a few packages to avoid conflicts and adding a few new explicit version requirements. Some of the new version constraints are probably too rigid and can be converted into >=; feel free to edit if so. The Jaxlib import is to ensure that a Cuda-compatible version is used, which does not happen by default. That might be too specific for this repository, so feel free to ignore that change.