Update sphinx_rtd_theme version

[trog-levrai]

Implements change requested in #6
Tested and now it works for me :)

[acroz]

Hey, thanks for the contribution!

I believe we pinned the sphinx-rtd-theme version as they changed how some of the CSS works in a way that messed up the theme in some places. I'll need to check if we need to do any fixes before merging this, which might not be very soon, sorry!

[trog-levrai]

Well it looks like the bar is actually working on your docs, maybe there is some workaround you are using to avoid this issue ?

[acroz]

No workaround unfortunately, your issue was the first I'd heard about this.

I imagine that it's working because we've not redeployed our docs for a while. According to the PR which implemented the fix, the issue was caused by changes in Sphinx 3.4, which was only released in late December.