fix: Fix using new_columns in scan_csv with compressed file

[nameexhaustion]

Fixes #19916

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 78.96%. Comparing base (62ebbe5) to head (40e98ff).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-lazy/src/scan/csv.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20412      +/-   ##
==========================================
- Coverage   78.97%   78.96%   -0.01%     
==========================================
  Files        1562     1562              
  Lines      220103   220096       -7     
  Branches     2486     2486              
==========================================
- Hits       173821   173809      -12     
- Misses      45709    45714       +5     
  Partials      573      573              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.