chore: allow phpunit 12

[Chris53897]

$currencies->setAccessible(true); is not needed anymore
Update: only since PHP 8.1 i have reverted that change

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4dd9a03) to head (2d706c2).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##                main       #42   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity         9         9           
===========================================
  Files              1         1           
  Lines             16        16           
===========================================
  Hits              16        16           

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