Test failures with sphinx 8.2.3

[mweinelt]

What version of myst-parser are you using?

4.0.1

What version dependencies are you using?

sphinx 8.2.3
docutils 0.21.2

What operating system are you using?

Linux

Describe the Bug

Test failures due to fixtures not being compatible with sphinx 8.2.3.

FAILED tests/test_renderers/test_fixtures_sphinx.py::test_sphinx_directives[320-math (`sphinx.directives.patches.MathDirective`):] - AssertionError: actual != expected (use --regen-file-failure)
FAILED tests/test_sphinx/test_sphinx_builds.py::test_references_singlehtml - AssertionError: FILES DIFFER:
FAILED tests/test_sphinx/test_sphinx_builds.py::test_extended_syntaxes - AssertionError: FILES DIFFER:
FAILED tests/test_sphinx/test_sphinx_builds.py::test_fieldlist_extension - AssertionError: FILES DIFFER:

Expected Behavior

Compatibility with recent Sphinx versions

To Reproduce

Update to sphinx 8.2.3 and run the test suite.