Update version of pyupgrade

[dstansby]

This updates the version of pyupgrade to match the minimum supported version of the package, and makes the corresponding pyupgrade fixes.

[codecov]

Codecov Report

Attention: Patch coverage is 97.22222% with 2 lines in your changes missing coverage. Please review.

Project coverage is 85.71%. Comparing base (56f72b0) to head (12bb6e5).

Files	Patch %	Lines
ome_zarr/csv.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #397      +/-   ##
==========================================
+ Coverage   85.44%   85.71%   +0.26%     
==========================================
  Files          13       13              
  Lines        1539     1540       +1     
==========================================
+ Hits         1315     1320       +5     
+ Misses        224      220       -4     

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