fix(rust): Fix unsoundness in group_tuples_perfect

[orlp]

Supersedes #19357.

[codecov]

Codecov Report

Attention: Patch coverage is 27.27273% with 48 lines in your changes missing coverage. Please review.

Project coverage is 80.21%. Comparing base (27289b2) to head (276713a).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-core/src/frame/group_by/perfect.rs	27.27%	48 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19359      +/-   ##
==========================================
+ Coverage   80.18%   80.21%   +0.02%     
==========================================
  Files        1523     1523              
  Lines      209897   209853      -44     
  Branches     2434     2434              
==========================================
+ Hits       168314   168330      +16     
+ Misses      41028    40968      -60     
  Partials      555      555              

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