Remove input/output prompts from rendered tutorials

[adrn]

This is only relevant once #153 is merged

We should remove the In[...] and Out[...] prompts from the rendered notebooks. This currently isn't possible with nbsphinx (see spatialaudio/nbsphinx#126). I've asked to see if they would consider adding an option (similar to what nbconvert has) to exclude the prompts, but we're stuck waiting for an upstream fix.

cc @kelle

[adrn]

This is partially solved - I added nbsphinx_prompt_width = 0 to the conf.py file and this seems to work by just hiding the HTML region that would display the prompt. I'll leave this issue open as a reminder that there may be a more elegant solution one day...

said every developer ever