Drop deprecated packaging metadata #142

Job	Run time
Verify dev env (ubuntu-latest)	14s
Verify dev env (windows-latest)	52s
Run linters	34s
Type-check package	19s
Verify dev env (macos-latest)	18s
Build docs & run doctests	28s
Tests on 3.8	1m 1s
Tests on 3.9	1m 4s
Tests on 3.10	1m 0s
Tests on 3.11	57s
Tests on 3.12	1m 9s
Tests on pypy-3.8	1m 52s
Tests on pypy-3.9	1m 4s
Combine & check coverage	6s
Ensure everything required is passing for branch protection	2s
	11m 0s

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