www/py-webargs: Update to 7.0.1

Changelog: https://github.com/marshmallow-code/webargs/blob/dev/CHANGELOG.rst#701-2020-12-14

PR: 252440
Submitted by: Goran Mekic <meka@tilda.center> (maintainer)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D28037