Test against pypy-3.12

[jwodder]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.31%. Comparing base (3977da8) to head (300859e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #48   +/-   ##
=======================================
  Coverage   99.31%   99.31%           
=======================================
  Files           6        6           
  Lines         583      583           
  Branches      117      117           
=======================================
  Hits          579      579           
  Misses          3        3           
  Partials        1        1           

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