Update data container notebook to reflect changes to pm.Data

[jessegrabowski]

pymc-devs/pymc#7047 depreciates pm.ConstantData and pm.MutableData (again), so the data container notebook no longer reflects best practices. It should be updated to:

1. Remove the explainer about the differences between MutableData and ConstantData, since it no longer exists, and;
2. Use pm.Data everywhere in the applied examples