2.6 and 2.6.1 yanked from PyPI

[Jarrod Millman]

Hi all,

I "yanked" 2.6 and 2.6.1 from PyPI:
https://pypi.org/help/#yanked

You can still install 2.6 and 2.6.1 (if you want) via:
- pip install networkx==2.6
and
- pip install networkx==2.6.1

We will release 2.6.3 (or maybe we will call it 2.7) once we resolve this PR:
- https://github.com/networkx/networkx/pull/4967

Best regards,
Jarrod