Update sphinx requirement from ^2.0 to ^3.1

[dependabot-preview]

Updates the requirements on sphinx to permit the latest version.

Changelog

Sourced from sphinx's changelog.

Release 3.1.0 (released Jun 08, 2020)

Dependencies

• #7746: mathjax: Update to 2.7.5

Incompatible changes

• #7477: imgconverter: Invoke "magick convert" command by default on Windows

Deprecated

• The first argument for sphinx.ext.autosummary.generate.AutosummaryRenderer has been changed to Sphinx object
• sphinx.ext.autosummary.generate.AutosummaryRenderer takes an object type as an argument
• The ignore argument of sphinx.ext.autodoc.Documenter.get_doc()
• The template_dir argument of sphinx.ext.autosummary.generate. AutosummaryRenderer
• The module argument of sphinx.ext.autosummary.generate. find_autosummary_in_docstring()
• The builder argument of sphinx.ext.autosummary.generate. generate_autosummary_docs()
• The template_dir argument of sphinx.ext.autosummary.generate. generate_autosummary_docs()
• The ignore argument of sphinx.util.docstring.prepare_docstring()
• sphinx.ext.autosummary.generate.AutosummaryRenderer.exists()
• sphinx.util.rpartition()

Features added

• LaTeX: Make the toplevel_sectioning setting optional in LaTeX theme
• LaTeX: Allow to override papersize and pointsize from LaTeX themes
• LaTeX: Add :confval:latex_theme_options to override theme options
• #7410: Allow to suppress "circular toctree references detected" warnings using :confval:suppress_warnings
• C, added scope control directives, :rst:dir:c:namespace, :rst:dir:c:namespace-push, and :rst:dir:c:namespace-pop.
• #2044: autodoc: Suppress default value for instance attributes
• #7473: autodoc: consider a member public if docstring contains :meta public: in info-field-list
• #7487: autodoc: Allow to generate docs for singledispatch functions by py:autofunction
• #7143: autodoc: Support final classes and methods
• #7384: autodoc: Support signatures defined by __new__(), metaclasses and

... (truncated)

Commits

• 62a9b32 Bump to 3.1.0 final
• 23a51a3 Merge pull request #7797 from tk0miya/7791_TypeError_for_singledispatchfunction
• d0cdf07 Update CHANGES for PR #7657
• 2ed2085 Merge pull request #7657 from mgeier/css-margins
• 7fa47e4 Merge pull request #7788 from tk0miya/7722_support_typevar
• bf89b1d Merge pull request #7794 from tk0miya/7792_setuptools_verbosity
• 588e5bd Merge pull request #7778 from tk0miya/7723_pdflatex_URL_having_singlequote
• f98987b Fix #7791: autodoc: TypeError is raised on documenting singledispatch function
• 8bd5f8b autodoc: Support TypeVar (refs: #7722)
• 6ccab6c Close #7792: setuptools: Support --verbosity option
• Additional commits viewable in compare view

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