docs: update superbowl example to align with the new version of Polars

[jrycw]

I've noticed the CI is failing due to the superbowl example. This PR updates the example to be compatible with the latest version of Polars.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.77%. Comparing base (b14c8f2) to head (a5c533a).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #460   +/-   ##
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  Coverage   86.77%   86.77%           
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  Files          42       42           
  Lines        4749     4749           
=======================================
  Hits         4121     4121           
  Misses        628      628           

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[jrycw]

@machow , I hadn’t noticed that you fixed this issue in #458. However, it seems there's still a deprecation warning:

/tmp/ipykernel_4495/1980599939.py:2: DeprecationWarning: The argument `columns` for `DataFrame.pivot` is deprecated. It has been renamed to `on`.
pl.DataFrame({"x": list(range(10))})

This is coming from the preview site.

[machow]

Ah thanks for catching the extra deprecated piece! Let's merge this, and then I'll take the commit out of the PR you mention