Update PolynomialRatio docs.

[kcin96]

This PR updates the docs for PolynomialRatio as per #415.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2637592) 97.46% compared to head (88900cd) 97.46%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #495   +/-   ##
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  Coverage   97.46%   97.46%           
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  Files          18       18           
  Lines        3080     3080           
=======================================
  Hits         3002     3002           
  Misses         78       78           

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[ViralBShah]

Bumping for a review.

[wheeheee]

I think this is quite clear. But if possible, I would like to merge #526 first, rebase, then remove the Polynomial. in these doctests so they pass?
Also, I'm not sure how GitHub keywords work; does @kcin96 need to edit their initial comment to mention that this closes #415 to close the issue automatically upon merge?

[ViralBShah]

We can just close the issue manually as well.

[wheeheee]

It seems the doctests fail for this part even without #526, so the Polynomial.s need to go even if we want to merge now.

[wheeheee]

fix doctests