devel/py-botocore: Update to version 1.4.70.

Changelog: https://github.com/boto/botocore/blob/1.4.70/CHANGELOG.rst

PR: 214159
Submitted by: bradleythughes@fastmail.fm (maintainer)
Approved by: swills (mentor)
Differential Revision: https://reviews.freebsd.org/D8442