docs(python): Change ordering of values in example for cum_max

[mdavis-xyz]

The example for cum_max uses an ascending sequence. So cum_max doesn't do anything in that case. In reverse mode it does the same as the non-cumulative sum. This change makes the example data go up and down, so the behaviour of the function is clearer.

(I wasn't able to build polars, even off the main branch. But this change is so trivial, I'm hoping it's fine anyway.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.44%. Comparing base (2357125) to head (f7fcfab).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16456      +/-   ##
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- Coverage   81.44%   81.44%   -0.01%     
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  Files        1409     1409              
  Lines      184725   184725              
  Branches     2971     2971              
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- Hits       150452   150447       -5     
- Misses      33753    33758       +5     
  Partials      520      520              

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[stinodego]

Good improvement, thanks!