Retire py-ipython5

[Adam <adam%netbsd.org@localhost>]

I would like to remove devel/py-ipython5. This is the last version that supports Python 2.7. I think all serious Python users already use devel/py-ipython (with Python 3.6+) and there is no point for keeping the old version around. The old iPython blocks some upgrades, like devel/py-traitlets, which would loose Python 2.7 compatibility.

Any objections?

Kind regards,
Adam