Orca build references non-existent mathjax dep

[BRONSOLO]

The mathjax download performed here: https://github.com/plotly/orca/blob/c68d3dfa7f293bc3035288dfc2941b4a7532ee14/deployment/Dockerfile#L85 will need to be updated as of: https://github.com/plotly/plotly.js/pull/5487.

Mathjax is now installed via npm in plotly.js here: https://github.com/plotly/plotly.js/pull/5494

FYI @antoinerg

[antoinerg]

@BRONSOLO is this blocking you?

[BRONSOLO]

Thanks @antoinerg! It's not blocking anything at the moment but will be a blocker if we ever have to make a new Orca release for 4.1.X so it would probably be safest to tackle sooner rather than later if possible (fyi @plotly/platform).