test: Use sharded repodata by default

[jjerphan]

Description

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 53.37%. Comparing base (666e3ed) to head (0135566).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4187      +/-   ##
==========================================
+ Coverage   52.88%   53.37%   +0.49%     
==========================================
  Files         239      239              
  Lines       29136    29136              
  Branches     3090     3090              
==========================================
+ Hits        15409    15552     +143     
+ Misses      13724    13581     -143     
  Partials        3        3              

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