Update sphinx requirement from <6.0 to <8.0

[dependabot]

Updates the requirements on sphinx to permit the latest version.

Release notes

Sourced from sphinx's releases.

Sphinx 7.2.2

Changelog: https://www.sphinx-doc.org/en/master/changes.html

Changelog

Sourced from sphinx's changelog.

Release 7.2.2 (released Aug 17, 2023)

Bugs fixed

• Fix the signature of the StateMachine.insert_input() patch, for when calling with keyword arguments.
• Fixed membership testing (in) for the :py:class:str interface of the asset classes (_CascadingStyleSheet and _JavaScript), which several extensions relied upon.
• Fixed a type error in SingleFileHTMLBuilder._get_local_toctree, includehidden may be passed as a string or a boolean.
• Fix :noindex: for PyModule and JSModule``.

Release 7.2.1 (released Aug 17, 2023)

Bugs fixed

• Restored the the :py:class:str interface of the asset classes (_CascadingStyleSheet and _JavaScript), which several extensions relied upon. This will be removed in Sphinx 9.
• Restored calls to Builder.add_{css,js}_file(), which several extensions relied upon.
• Restored the private API TocTree.get_toctree_ancestors(), which several extensions relied upon.

Release 7.2.0 (released Aug 17, 2023)

Dependencies

• #11511: Drop Python 3.8 support.
• #11576: Require Pygments 2.14 or later.

Deprecated

• #11512: Deprecate sphinx.util.md5 and sphinx.util.sha1. Use hashlib instead.
• #11526: Deprecate sphinx.testing.path. Use os.path or pathlib instead.
• #11528: Deprecate sphinx.util.split_index_msg and sphinx.util.split_into. Use sphinx.util.index_entries.split_index_msg instead.
• Deprecate sphinx.builders.html.Stylesheet and sphinx.builders.html.Javascript. Use sphinx.application.Sphinx.add_css_file()

... (truncated)

Commits

• ed84d63 Bump to 7.2.2 final
• ea4a73e [bot]: Update message catalogues (#11612)
• e47846a Fix :noindex: for PyModule and JSModule``
• b2fc47f Add CHANGES entry for renaming the StateMachine.insert_input() parameter
• 0835c3e Fix regression in SingleFileHTMLBuilder._get_local_toctree
• 49dc0dd Fix asset class string interface membership testing
• 8512855 Fix signature of docutils include_source monkeypatch (#11610)
• e1d9068 Bump version
• 441a9e4 Bump to 7.2.1 final
• ec31853 Restore TocTree.get_toctree_ancestors()
• Additional commits viewable in compare view

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[mjurbanski-reef]

@dependabot rebase

[dependabot]

Looks like sphinx is no longer a dependency, so this is no longer needed.