Prevent return inferencedata error + cheater/liar fix

[toppare]

The default of return_inferencedata was False but in the future (v4.0) it will be True. However, the rest of the code is written for False case so I changed all pm.sample to have an explicit False.

Currently it shows this warning:

FutureWarning: In v4.0, pm.sample will return an arviz.InferenceData object instead of a MultiTrace by default. You can pass return_inferencedata=True or return_inferencedata=False to be safe and silence this warning

-> Also a small change in the text in Ch2 as we are actually modeling the cheaters and not liars.