fix(python): Raise if pass a negative n into clear

[reswqa]

This aligns the behavior of series.clear(-1) and df.clear(-1).

NB. Before this change, the error of df.clear(-1) is raised from the extend_constant(pass a negative n), I think a more explicit error would be nice.

The only difference is that for an empty series, passing a negative n does not throw an error before this change. I feel like it makes the function behave a bit more predictable if we reject n < 0 outright, WDYT?

This fixes #15421.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.13%. Comparing base (758b55a) to head (bab7462).
Report is 9 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15432      +/-   ##
==========================================
- Coverage   81.13%   81.13%   -0.01%     
==========================================
  Files        1362     1362              
  Lines      174802   174824      +22     
  Branches     2531     2532       +1     
==========================================
+ Hits       141825   141842      +17     
- Misses      32493    32498       +5     
  Partials      484      484              

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[stinodego]

Thanks! I made a minor update to the error message formatting.