fix: Clear stale negative cache entries

[jjerphan]

Description

Tentative fix for #4322.

Fix failures observed in Code Coverage workflows.

Type of Change

• Bugfix
• Feature / enhancement
• CI / Documentation
• Maintenance

Checklist

• My code follows the general style and conventions of the codebase, ensuring consistency
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have run pre-commit run --all locally in the source folder and confirmed that there are no linter errors.
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes

[codecov]

Codecov Report

❌ Patch coverage is 54.71698% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.26%. Comparing base (df10fc2) to head (ff808f1).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
libmamba/src/core/transaction.cpp	0.00%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4328      +/-   ##
==========================================
+ Coverage   55.38%   56.26%   +0.88%     
==========================================
  Files         243      243              
  Lines       30374    30429      +55     
  Branches     3257     3265       +8     
==========================================
+ Hits        16822    17122     +300     
+ Misses      13549    13304     -245     
  Partials        3        3              

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