www/py-django-configurations: Deprecate/Set to expire

• The project is no longer maintained by upstream, and an alternative, py-django-configurator, has been available for some time now.
  
  There are no consumers left in the ports tree as well.

• Set CONFLICTS_INSTALL while I'm here, because py-django-configurator was recently added to the ports tree.

PR: 291707
With hat: python