build: drop python 3.7

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (d5fa29a) 95.43% compared to head (cc350b2) 95.42%. Report is 1 commits behind head on main.

:exclamation: Current head cc350b2 differs from pull request most recent head deba232. Consider uploading reports for the commit deba232 to get more accurate results

Files	Patch %	Lines
src/nd2/__init__.py	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #208 +/- ## ========================================== - Coverage 95.43% 95.42% -0.01% ========================================== Files 17 17 Lines 2346 2319 -27 ========================================== - Hits 2239 2213 -26 + Misses 107 106 -1 ```

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[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #208 will not alter performance

_{Comparing drop37 (deba232) with main (d5fa29a)}

Summary

✅ 13 untouched benchmarks