www/py-django-widget-tweaks: Update to 1.4.8

• Also assign the port to Django 2.2 (current LTS release) as Django 1.11 is End-of-Life.

• Set Python 3.6 as minimum version because support for Python 3.5 was dropped with the 1.4.6 release.

• Pet portlint (Tweak length of COMMENT, sort variables according to the PHB and fix trailing whitespace in pkg-descr).

Changelog:

https://github.com/jazzband/django-widget-tweaks/blob/1.4.8/CHANGES.rst

PR: 246172
Approved by: <rozhuk.im@gmail.com> (maintainer)