Update MvGaussianRandomWalk notebook to v5 (#518)

* Draft update of BNN notebook

* Pre-commit fixes

* Address reviewer comments

* Update MvGaussianRandomWalk_demo to v5

* Cleanup

* Fixed docs reference

* Fixed docs reference

* Fixed doc link

Co-authored-by: Oriol Abril-Pla <oriol.abril.pla@gmail.com>

* Added footer

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Co-authored-by: Oriol Abril-Pla <oriol.abril.pla@gmail.com>

Author: fonnesbeck