Update sphinx to 1.8.4

[pyup-bot]

This PR updates sphinx from 1.8.3 to 1.8.4.

Changelog

1.8.4

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

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

* 3707: latex: no bold checkmark (✔) available.
* 5605: with the documentation language set to Chinese, English words could not
be searched.
* 5889: LaTeX: user ``numfig_format`` is stripped of spaces and may cause
build failure
* C++, fix hyperlinks for declarations involving east cv-qualifiers.
* 5755: C++, fix duplicate declaration error on function templates with constraints
in the return type.
* C++, parse unary right fold expressions and binary fold expressions.
* pycode could not handle egg files on windows
* 5928: KeyError: 'DOCUTILSCONFIG' when running build
* 5936: LaTeX: PDF build broken by inclusion of image taller than page height
in an admonition
* 5231: "make html" does not read and build "po" files in "locale" dir
* 5954: ``:scale:`` image option may break PDF build if image in an admonition
* 5966: mathjax has not been loaded on incremental build
* 5960: LaTeX: modified PDF layout since September 2018 TeXLive update of
:file:`parskip.sty`
* 5948: LaTeX: duplicated labels are generated for sections
* 5958: versionadded directive causes crash with Python 3.5.0
* 5995: autodoc: autodoc_mock_imports conflict with metaclass on Python 3.7
* 5871: texinfo: a section title ``.`` is not allowed

Links

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