Hierarchical NB has missing images

[twiecki]

https://docs.pymc.io/pymc-examples/examples/generalized_linear_models/GLM-hierarchical.html

Missing are the images of the hierarchical model that @fonnesbeck created. Not sure if he has an updated link.

[saiwing-yeung]

Same for https://github.com/pymc-devs/pymc-examples/blob/main/examples/case_studies/multilevel_modeling.ipynb
in the ## Multilevel and hierarchical models cell.

[drbenvincent]

This is not fixed yet.

New notebook location with new website: https://github.com/pymc-devs/pymc-examples/blob/main/examples/generalized_linear_models/GLM-hierarchical.ipynb

Still needs to be updates to best practices.