www/py-django-bootstrap-pagination: Switch to Django 3.2

• Adjust RUN_DEPENDS to use Django 3.2 (LTS release) because the extended support for Django 3.0 has expired on 6th April 2021.

• Also avoid the installation of the test suite into the root of Python's site-lib directory as it can lead to conflicts with other packages.

PR: 255114
Approved by: dbaio (maintainer)