Prepare for PyMC 5.16 release

This new release has breaking changes because of the latest version of PyTensor. We are "solving" this by having an upper bound on the PyMC version, see https://github.com/pymc-labs/pymc-marketing/pull/725

The updates we need to do are [(only) here (?)](https://github.com/pymc-labs/pymc-marketing/blob/6edc4ca4e9353d10804c8817252a7e45879c0827/pymc_marketing/clv/distributions.py)