docs: Fix minor rogue apostrophes

[mcrumiller]

Super minor, removes some apostrophes that shouldn't be there.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.89%. Comparing base (262f7bc) to head (aa08c62).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...ates/polars-core/src/series/arithmetic/borrowed.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18865      +/-   ##
==========================================
+ Coverage   79.87%   79.89%   +0.01%     
==========================================
  Files        1519     1519              
  Lines      205839   205839              
  Branches     2898     2898              
==========================================
+ Hits       164416   164456      +40     
+ Misses      40875    40835      -40     
  Partials      548      548              

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[rodrigogiraoserrao]

Thanks. Looks good to me.