docs: unbreak RTD and fix GitHub CI #175

Job	Run time
Tests on paywalled platforms (macos-13-xlarge, 3.12)	50s
Tests on other platforms (windows-2019, 3.10)	3m 6s
Tests on other platforms (windows-2022, 3.11)	3m 0s
Tests on other platforms (windows-2022, 3.12)	2m 37s
Tox test (py38)	2m 2s
Tests on other platforms (macos-12, 3.11)	2m 30s
Tox test (py39)	2m 5s
Tests on other platforms (macos-13, 3.12)	1m 47s
Tox test (py310)	1m 59s
Tox test (py311)	2m 0s
Tox test (py312-cover)	3m 11s
Tox test (docs, graphviz)	1m 50s
PyPI packaging	0s
Docker image	0s
	26m 57s

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