Make palettize work on numpy 2.0.

[gerritholl]

Make palettize work on numpy 2.0.

• Closes palettize fails in numpy2 #175 (remove if there is no corresponding issue, which should only be the case for minor changes)
• Tests added (for all bug fixes or enhancements)
• Tests passed (for all non-documentation changes)
• Passes git diff origin/master **/*py | flake8 --diff (remove if you did not edit any Python files)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.54%. Comparing base (8b71319) to head (9139dee).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #176      +/-   ##
==========================================
+ Coverage   91.53%   91.54%   +0.01%     
==========================================
  Files          11       11              
  Lines        4062     4068       +6     
==========================================
+ Hits         3718     3724       +6     
  Misses        344      344              

Flag	Coverage Δ
unittests	91.54% <100.00%> (+0.01%)	⬆️

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[coveralls]

coverage: 91.79% (+0.01%) from 91.777%
when pulling 9139dee on gerritholl:bugfix-palettize-np2
into c665c4d on pytroll:main.

[mraspaud]

LGTM, thanks for spotting and fixing this.