Inconsistent TF requirement (static vs runtime)

[jonas-eschle]

There seems to be some inconsistency with the required versions: setup.py requires TF >= 2.16, while the __init__.py runtime dependency check requires 2.18.

This leads to a simple failure when installing pip install tensorflow-probability[tf] "tensorflow<2.18" (where the constraint could come from any other package, it's just here for a minimal example)

What is the right choice?