Update sphinx requirement from <8 to <9 (#484) #1295

Job	Run time
Self-Check	11s
ensure-catalog-matches-hook-config	18s
Run 'mypy' on python 3.x	22s
Run tests on ubuntu-latest, py3.8	1m 31s
Run 'twine-check' on python 3.x	17s
test-sdist	1m 38s
Run tests on ubuntu-latest, py3.9	1m 27s
Run 'py-mindeps' on python 3.8	24s
Run tests on ubuntu-latest, py3.10	1m 34s
Run tests on ubuntu-latest, py3.11	1m 30s
Run tests on ubuntu-latest, py3.12	1m 43s
Run tests on windows-latest, py3.8	2m 23s
Run tests on windows-latest, py3.9	2m 54s
Run tests on windows-latest, py3.10	2m 30s
Run tests on windows-latest, py3.11	2m 30s
Run tests on windows-latest, py3.12	2m 46s
Run tests on macos-latest, py3.8	1m 55s
Run tests on macos-latest, py3.9	1m 6s
Run tests on macos-latest, py3.10	1m 19s
Run tests on macos-latest, py3.11	1m 17s
Run tests on macos-latest, py3.12	1m 29s
Collate results to check for skipped tests	8s
	31m 12s

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