py-graphviz: updated to 0.20.1

Version 0.20.1
--------------
Fix documentation building: upgrade to Sphinx 5.0.

Fix broken user guide links in API documentation.

Version 0.20
------------
Add keyword-only ``neato_no_op`` argument to ``.render()``, ``.pipe()``,
and stand-alone ``graphviz.render()`` and ``graphviz.pipe()``.

When building a ``Graph`` or ``Digraph``,
warn about an expected DOT syntax error in rendering
when passing a string that ends with an odd number of backslashes
(e.g. invalid ``dot.node('spam', label='\\')``
instead of correct ``..., label=r'\\'``
for a node labled as a backslash).

Increase visibility of ``graphviz.escape()`` in the documentation.


(adam)