Drop support for python 3.9

[delucchi-cmu]

Support dropped in hats. See astronomy-commons/hats#442

[github-actions]

Before [38a77f9] <v0.4.4>	After [9ec109f]	Ratio	Benchmark (Parameter)
failed	failed	n/a	benchmarks.time_box_filter_on_partition
failed	failed	n/a	benchmarks.time_polygon_search
1.86±0.01s	1.87±0.02s	1.01	benchmarks.time_create_midsize_catalog
12.6±0.03s	12.6±0.03s	0.99	benchmarks.time_create_large_catalog
86.9±2ms	85.1±2ms	0.98	benchmarks.time_kdtree_crossmatch

Click here to view all benchmarks.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.40%. Comparing base (38a77f9) to head (74dfbf1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #527   +/-   ##
=======================================
  Coverage   97.40%   97.40%           
=======================================
  Files          43       43           
  Lines        1697     1697           
=======================================
  Hits         1653     1653           
  Misses         44       44           

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