Drop deprecated packaging metadata (#69) #144

Job	Run time
Build docs & run doctests	23s
Run linters	29s
Verify dev env (ubuntu-latest)	20s
Type-check package	32s
Verify dev env (windows-latest)	38s
Tests on 3.8	59s
Verify dev env (macos-latest)	19s
Tests on 3.9	1m 4s
Tests on 3.10	1m 2s
Tests on 3.11	55s
Tests on 3.12	1m 4s
Tests on pypy-3.8	2m 11s
Tests on pypy-3.9	1m 9s
Combine & check coverage	13s
Ensure everything required is passing for branch protection	2s
	11m 20s

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