Update sphinx to 2.4.4

[pyup-bot]

This PR updates Sphinx from 2.4.3 to 2.4.4.

Changelog

2.4.4

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

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

* 7197: LaTeX: platex cause error to build image directive with target url
* 7223: Sphinx builds has been slower since 2.4.0

Links

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

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[coveralls]

Coverage remained the same at 82.459% when pulling 8fb6d8a on pyup-update-sphinx-2.4.3-to-2.4.4 into 54ba1d9 on develop.