Tweak README #544

Job	Run time
Test with python 3.6 on windows-latest	2m 3s
Test with python 3.7 on windows-latest	1m 22s
Test with python 3.8 on windows-latest	9m 21s
Test with python 3.12 on windows-latest	9m 25s
Test with python 3.6 on macos-latest	2m 49s
Test with python 3.7 on macos-latest	3m 18s
Test with python 3.8 on macos-latest	3m 29s
Test with python 3.12 on macos-latest	10m 33s
Test with python 2.7 on ubuntu-20.04	29s
Test with python 3.6 on ubuntu-20.04	36s
Test with python 3.7 on ubuntu-latest	34s
Test with python 3.8 on ubuntu-latest	3m 19s
Test with python 3.9 on ubuntu-latest	3m 33s
Test with python 3.10 on ubuntu-latest	3m 20s
Test with python 3.11 on ubuntu-latest	3m 8s
Test with python 3.12 on ubuntu-latest	5m 20s
	1h 2m 39s

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