build: drop python 3.8

[tlambert03]

will cover adding python 3.13 in #260

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.84%. Comparing base (31c7830) to head (6ede683).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #268      +/-   ##
==========================================
+ Coverage   86.77%   86.84%   +0.07%     
==========================================
  Files          25       25              
  Lines        1255     1262       +7     
==========================================
+ Hits         1089     1096       +7     
  Misses        166      166              

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[codspeed-hq]

CodSpeed Performance Report

Merging #268 will improve performances by 15.23%

_{Comparing drop38 (6ede683) with main (31c7830)}

Summary

⚡ 2 improvements
✅ 7 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	drop38	Change
⚡	test_time_from_dict_to_ome[med]	28.8 ms	25.1 ms	+14.55%
⚡	test_time_from_dict_to_ome[small]	2.5 ms	2.2 ms	+15.23%