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 <[email protected]>

* Added footer

---------

Co-authored-by: Oriol Abril-Pla <[email protected]>

Author: fonnesbeck