security/py-{acme,certbot}: update to 0.11.1

• Update PORTVERSION and distinfo checksum (0.11.1)
• Update WWW in py-acme/pkg-descr
• Rename py-letsencrypt to py-certbot in py-certbot/pkg-message

Approved by: koobs (maintainer timeout 17 days, py-certbot)
Differential Revision: D9421