fix(python): Fix drop selector

[ritchie46]

fixes #18016

[alexander-beedie]

Beat me to it 😆👍
I'll see if I can remove/clean-up some other uses of expand_selector this week.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 80.45%. Comparing base (d5265d3) to head (660a144).
Report is 9 commits behind head on main.

Files	Patch %	Lines
...polars-plan/src/plans/conversion/expr_expansion.rs	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18034      +/-   ##
==========================================
- Coverage   80.49%   80.45%   -0.05%     
==========================================
  Files        1496     1496              
  Lines      196786   197164     +378     
  Branches     2817     2820       +3     
==========================================
+ Hits       158407   158632     +225     
- Misses      37858    38010     +152     
- Partials      521      522       +1     

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[ritchie46]

Beat me to it 😆👍

😎

I'll see if I can remove/clean-up some other uses of expand_selector this week.

Nice. It should speed up query building for the power users. :)