py-sphinx: updated to 4.3.1

Release 4.3.1 (released Nov 28, 2021)

Features added
* mathjax: Support chnaging the loading method of MathJax to ���defer��� via mathjax_options
Bugs fixed
* autodoc: AttributeError is raised on building document for functions decorated by functools.lru_cache
* autodoc: AttributeError is raised on building document for an object having invalid __doc__ atribute
* autodoc: Failed to process a function wrapped with functools.partial if autodoc_preserve_defaults enabled
* html: Class namespace collision between autodoc signatures and docutils-0.17
* imgmath: Crashed if the dvisvgm command failed to convert equation
* mathjax: Failed to render equations via MathJax v2. The loading method of MathJax is back to ���async��� method again

(adam)