Notebooks use "images/" instead of "figures/" for Markdown images

[nitya]

Static images are in the notebooks/figures folder (and referenced with this path in the website) - but the Notebooks themselves use images/ as the folder prefix in Markdown cells referencing the figures. I am assuming figures/ is the right name and the notebooks need to be updated.

I made the fixes in my local fork to verify they worked (happy to submit a PR) but wanted to check if that was the preferred fix or if you wanted to just rename the figures/ folder instead.