Update sphinx to 4.0.3

[pyup-bot]

This PR updates sphinx from 4.0.2 to 4.0.3.

Changelog

4.0.3

=====================================

Features added
--------------

* C, add C23 keywords ``_Decimal32``, ``_Decimal64``, and ``_Decimal128``.
* 9354: C, add :confval:`c_extra_keywords` to allow user-defined keywords
during parsing.
* Revert the removal of ``sphinx.util:force_decode()`` to become some 3rd party
extensions available again during 5.0

Bugs fixed
----------

* 9330: changeset domain: :rst:dir:`versionchanged` with contents being a list
will cause error during pdf build
* 9313: LaTeX: complex table with merged cells broken since 4.0
* 9305: LaTeX: backslash may cause Improper discretionary list pdf build error
with Japanese engines
* 9354: C, remove special macro names from the keyword list.
See also :confval:`c_extra_keywords`.
* 9322: KeyError is raised on PropagateDescDomain transform

Links

• PyPI: https://pypi.org/project/sphinx
• Changelog: https://pyup.io/changelogs/sphinx/
• Homepage: http://sphinx-doc.org/

[pyup-bot]

Closing this in favor of #1629