Update sphinx requirement from ~=2.3 to ~=4.0

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Updates the requirements on sphinx to permit the latest version.

Changelog

Sourced from sphinx's changelog.

Release 4.0.0 (released May 09, 2021)

Dependencies

4.0.0b1

• Drop python 3.5 support
• Drop docutils 0.12 and 0.13 support
• LaTeX: add tex-gyre font dependency

4.0.0b2

• Support docutils-0.17. Please notice it changes the output of HTML builder. Some themes do not support it, and you need to update your custom CSS to upgrade it.

Incompatible changes

4.0.0b1

• #8539: autodoc: info-field-list is generated into the class description when autodoc_typehints='description' and autoclass_content='class' set
• #8898: extlinks: "%s" becomes required keyword in the link caption string
• domain: The Index class becomes subclasses of abc.ABC to indicate methods that must be overrided in the concrete classes
• #4826: py domain: The structure of python objects is changed. A boolean value is added to indicate that the python object is canonical one
• #7425: MathJax: The MathJax was changed from 2 to 3. Users using a custom MathJax configuration may have to set the old MathJax path or update their configuration for version 3. See :mod:sphinx.ext.mathjax.
• #7784: i18n: The msgid for alt text of image is changed
• #5560: napoleon: :confval:napoleon_use_param also affect "other parameters" section
• #7996: manpage: Make a section directory on build manpage by default (see :confval:man_make_section_directory)
• #7849: html: Change the default setting of :confval:html_codeblock_linenos_style to 'inline'
• #8380: html search: search results are wrapped with <p> instead of <div>
• html theme: Move a script tag for documentation_options.js in basic/layout.html to script_files variable
• html theme: Move CSS tags in basic/layout.html to css_files variable
• #8915: html theme: Emit a warning for sphinx_rtd_theme-0.2.4 or older
• #8508: LaTeX: uplatex becomes a default setting of latex_engine for Japanese documents
• #5977: py domain: :var:, :cvar: and :ivar: fields do not create cross-references

... (truncated)

Commits

• a317d00 Bump to 4.0.0 final
• 09bb986 Update message catalogs
• 50d027a Update CHANGES for PR #9167
• a0d6036 Merge pull request #9167 from bonartm/fix_css_specific_page
• a7c5a3a fix missing underscore
• cfb9183 Update dependency: jinja2 < 3.0 and MarkupSafe < 2.0
• 53c6353 Merge pull request #9163 from tk0miya/extlinks_warning
• 8d54010 Fix test: deprecation warning for extlinks
• 742a2e0 Bump version
• 07e8475 Bump to 4.0.0 beta2
• Additional commits viewable in compare view

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[codecov[bot]]

Codecov Report

Merging #135 (7365893) into master (1909ee9) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #135   +/-   ##
=======================================
  Coverage   82.76%   82.76%           
=======================================
  Files          28       28           
  Lines        2849     2849           
  Branches      492      492           
=======================================
  Hits         2358     2358           
  Misses        359      359           
  Partials      132      132           

Flag	Coverage Δ
CPython	82.73% <ø> (ø)
Linux	82.73% <ø> (ø)
PyPy	82.20% <ø> (ø)
v3.6	82.21% <ø> (ø)
v3.7	82.20% <ø> (ø)
v3.8	82.64% <ø> (ø)
v3.9	82.64% <ø> (ø)

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