⬆️ Update sphinx requirement from <9,>=8 to >=8,<10 #1899

Job	Run time
pre-commit	17s
Check myst-docutils install (0.20)	14s
Check myst-docutils install (0.21)	15s
pytest: py3.11, sphinx>=8,<9, on ubuntu-latest	34s
pytest: py3.13, sphinx>=8,<9, on ubuntu-latest	38s
pytest: py3.12, sphinx>=8,<9, on ubuntu-latest	41s
pytest: py3.11, sphinx>=8,<9, on windows-latest	1m 24s
check	3s
Publish myst-parser to PyPi	0s
Publish myst-docutils to PyPi	0s
	4m 6s

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