fix: weights should not be raised to the power n in the n-th moment calculation

[ikrommyd]

Closes #3722

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.71%. Comparing base (b749e49) to head (0195c4b).
⚠️ Report is 467 commits behind head on main.

Additional details and impacted files

Files with missing lines	Coverage Δ
src/awkward/operations/ak_moment.py	92.85% <ø> (+0.85%)	⬆️

... and 199 files with indirect coverage changes

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[github-actions]

The documentation preview is ready to be viewed at http://preview.awkward-array.org.s3-website.us-east-1.amazonaws.com/PR3729

[ianna]

@ikrommyd - thanks for jumping in. Let’s discuss this at the next meeting. Thanks