multiple ports: Update MAINTANER

Change bradleythughes@fastmail.fm -> bhughes@FreeBSD.org after
receiving my ports commit bit on all ports I maintain: devel/awscli,
devel/py-botocore, net/py-s3transfer, net/turnserver, www/node4,
www/node6, and www/node.

Approved by: robak (mentor)
Differential Review: https://reviews.freebsd.org/D11015