graphics/py-OWSLib: Update to 0.19.2

• Update to 0.19.2
• Python 3.5 support is dropped upstream

Changelog:

https://github.com/geopython/OWSLib/blob/master/CHANGES.rst#0192-2020-03-13

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D24396