build: drop support for python3.7

[tlambert03]

@erickmartins, not sure if this will affect you? I'd like ome-types v0.5.0 to be the last series to support python3.7

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8df7874) 86.69% compared to head (47ca615) 86.67%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #245      +/-   ##
==========================================
- Coverage   86.69%   86.67%   -0.03%     
==========================================
  Files          24       24              
  Lines        1203     1201       -2     
==========================================
- Hits         1043     1041       -2     
  Misses        160      160              

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[codspeed-hq]

CodSpeed Performance Report

Merging #245 will not alter performance

_{Comparing drop37 (47ca615) with main (8df7874)}

Summary

✅ 9 untouched benchmarks

[erickmartins]

omero-cli-transfer is already python_requires='>=3.8', so you're good to go!