Compatibility with python-xxhash v4.0

[trexfeathers]

Description

Closes #7251. This will not show up in our CI (conda-based) until conda-forge/python-xxhash-feedstock#46 is merged. But I have tested locally.

Targeting v3.16.x since this is planned to be issued as part of a patch release.

Checklist

Important

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• Included a What's New entry
• Incorporated type hints in any changed code
• Checked if tests need updating
• Checked if benchmarks need updating
• Checked if documentation needs updating
  • Docstrings (we love code examples!)
  • User Manual pages
• Checked if dependencies need updating
• Confirmed that the GitHub 'checks' on this PR are passing ✅
  (further reading)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.42%. Comparing base (f427270) to head (6ba18f4).

Additional details and impacted files

@@           Coverage Diff            @@
##           v3.16.x    #7262   +/-   ##
========================================
  Coverage    90.42%   90.42%           
========================================
  Files           93       93           
  Lines        25812    25814    +2     
  Branches      4795     4796    +1     
========================================
+ Hits         23340    23342    +2     
  Misses        1693     1693           
  Partials       779      779           

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[pp-mo]

LGTM

I was going to say we should definitely use a utf8 encoding,
but I now see that is the default anyway.