Update to use recent versions of Sphinx #824

Job	Run time
Run linters with pre-commit	1m 10s
Determine Python versions	4s
Test building the documentation	2m 6s
Python 3.12 on ubuntu-20.04 (standalone: false, 32bit: false)	22m 53s
Python 3.12 on ubuntu-20.04 (standalone: false, 32bit: true)	22m 51s
Python 3.12 on ubuntu-20.04 (standalone: true, 32bit: false)	22m 54s
Python 3.12 on ubuntu-20.04 (standalone: true, 32bit: true)	21m 59s
Python 3.12 on windows-2019 (standalone: false, 32bit: false)	22m 47s
Python 3.12 on windows-2019 (standalone: false, 32bit: true)	22m 49s
Python 3.12 on windows-2019 (standalone: true, 32bit: false)	22m 47s
Python 3.12 on windows-2019 (standalone: true, 32bit: true)	22m 46s
Python 3.12 on macOS-11 (standalone: false, 32bit: false)	22m 49s
Python 3.12 on macOS-11 (standalone: false, 32bit: true)	22m 49s
Python 3.12 on macOS-11 (standalone: true, 32bit: false)	22m 49s
Python 3.12 on macOS-11 (standalone: true, 32bit: true)	22m 50s
Python 3.9 on ubuntu-20.04 (standalone: false, 32bit: false)	22m 52s
Python 3.9 on ubuntu-20.04 (standalone: true, 32bit: false)	21m 19s
Indicate completion to coveralls.io	1s
	5h 20m 35s

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