www/py-django22: Deprecate and set to expire

Set a deprecation note and let it expire to the end of June to give
enough time to switch all affected ports over to Django 3.2 which is the
next LTS release.

PR: 261313
Reviewed by: koobs
Approved by: dbaio, sunpoet (python, maintainer)
Differential Revision: https://reviews.freebsd.org/D33793