Upgrade community/py3-pydot and community/py3-pygraphviz

This PR upgrade community/py3-pydot from 1.4.1 to 2.0.0 and community/py3-pygraphviz from 1.10 to 1.13. Both of these packages are optional dependencies of community/py3-networkx and are below the minimum version required by networkx.

This PR removes the py3-pygraphviz-doc subpackage because it wasn't actually docs. The subpackage just contained some example code; building pygraphviz's actual documentation depends on some packages not yet in aports.