Update PolicyEngine bundle to 6.6.0

[policyengine]

Summary

Update PolicyEngine .py bundle from 6.5.0 to 6.6.0.

Bundled versions

• policyengine: 6.6.0
• policyengine-core: 3.33.0
• policyengine-us: 2.2.1
• policyengine-uk: 2.130.1
• spm-calculator: 1.0.0

Certified data releases

• US: populace-us-2024-spm-20260915
• UK: policyengine-uk-data-1.58.1

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.62%. Comparing base (71dba65) to head (5ad6614).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3947   +/-   ##
=======================================
  Coverage   47.62%   47.62%           
=======================================
  Files         239      239           
  Lines       13425    13425           
  Branches     2318     2318           
=======================================
  Hits         6393     6393           
  Misses       6395     6395           
  Partials      637      637           

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