Fix Periodogram pickling

[hombit]

No description provided.

[codspeed-hq]

CodSpeed Performance Report

Merging #532 will not alter performance

_{Comparing periodogram-power-pickle (12546c7) with master (2a34273)}

Summary

✅ 106 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 6 lines in your changes missing coverage. Please review.

Project coverage is 84.93%. Comparing base (2a34273) to head (12546c7).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
light-curve/src/features.rs	72.72%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #532      +/-   ##
==========================================
+ Coverage   84.81%   84.93%   +0.12%     
==========================================
  Files           9        9              
  Lines        2845     2848       +3     
==========================================
+ Hits         2413     2419       +6     
+ Misses        432      429       -3     

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