Tests

Remove test dependency on unmaintained PyPI toml package (#117) #571

Job	Run time
Run all tests (3.13 on ubuntu-latest)	7m 38s
Run important tests (pypy-3.10 on ubuntu-latest)	2m 49s
Run important tests (pypy-3.7 on ubuntu-latest)	3m 28s
Run important tests (3.7 on ubuntu-22.04)	1m 13s
Run important tests (3.13 on macos-latest)	1m 21s
Run important tests (3.13 on windows-latest)	3m 20s
Tests done	27s
	20m 16s

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