Python: add usetex to plot_to_fig call

[rmcdermo]

No description provided.

[mcgratta]

Do we add use_tex=True or usetex=True to the list of arguments on the fds_plot_to_fig line?

[rmcdermo]

usetex=True. See compression_wave.py

In general, try to avoid using this. For now, I am just testing. I think I can get the super and sub scripts to work without it. So, you should eventually only need this for more complex latex labels.