Update sphinx to 2.4.2

[pyup-bot]

This PR updates Sphinx from 2.4.1 to 2.4.2.

Changelog

2.4.2

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

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

* 7138: autodoc: ``autodoc.typehints`` crashed when variable has unbound object
as a value
* 7156: autodoc: separator for keyword only arguments is not shown
* 7146: autodoc: IndexError is raised on suppressed type_comment found
* 7161: autodoc: typehints extension does not support parallel build
* 7178: autodoc: TypeError is raised on fetching type annotations
* 7151: crashed when extension assigns a value to ``env.indexentries``
* 7170: text: Remove debug print
* 7137: viewcode: Avoid to crash when non-python code given

Links

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