remove old location of notebook from examples

[MarcoGorelli]

GLM-hierarchical-advi-minibatch appears twice in the table of contents, both in

generalized_linear_models/GLM-hierarchical-advi-minibatch

and in

variational_inference/GLM-hierarchical-advi-minibatch

The latter is correct.

Eventually, there should probably be a CI job in PyMC3 which builds the docs and would catch this kind of error (which prevents the docs from being built)

[AlexAndorra]

Thanks @MarcoGorelli !