devel/py-django-tastypie-mongoengine: Fix RUN_DEPENDS

• Assign the port to Django 2.2 (current LTS release) to unbreak the build when testing the RUN_DEPENDS.
  
  This should have already been done in r531187 when I updated and assigned www/py-django-tastypie to Django 2.2.

• Bump PORTREVISION for dependency change.

Pointy hat: kai
Approved by: portmgr blanket