devel/py-pyasn1-modules: update to 0.3.0

• update to 0.3.0
• switch to pep517
• update homepage link

Original author of pysnmp1 Ilya Etingof has passed away:
https://github.com/etingof/pyasn1-modules/issues/154

and all pysnmp related project were moved community-driven one.

PR: 272561
Reported by: Alastair Hogge <agh@riseup.net>