doc: mathjax 404 prevents proper rendering of math expressions

[d-v-b]

Mathematical expressions in the deployed docs are not being rendered correctly for me (see example below):

I believe this is caused by mathjax not being fetched -- it looks like the deployed site is attempting to get mathjax from https://google.github.io/tensorstore/_static/mathjax/tex-mml-chtml.js, which 404s.