Remove InferenceData object warning from v4

[twiecki]

Currently v4 still displays:

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.

when calling pm.sample(). Need to remove and set return_inferencedata=True.

[michaelosthege]

The issue exists already and is part of the v4 milestone: #4372

[michaelosthege]

Closed by 0923d25