Deal with rounding errors in superiority.py

[Expertium]

Sometimes, as a result of rounding, the values in some cells don't add up to 100.0%, and add up to 100.1% instead. Example:

I fixed that. This change requires re-generating the diagram.

[L-M-Sherlock]

Could you update the image?

[Expertium]

I can update it in README, but you'll have to add it to plots yourself.

[L-M-Sherlock]

Fine. I will add it tomorrow.