Apply multi-arch hints.

+ python-django-postgres-extra-doc: Add Multi-Arch: foreign.

Changes-By: apply-multiarch-hints

debian/control

@@ -27,6 +27,7 @@ Architecture: all
 Depends:
  ${misc:Depends},
  ${sphinxdoc:Depends},
+Multi-Arch: foreign
 Description: Extended PostgreSQL for Django (Documentation)
  This provides extended functionality for PostgreSQL databases to Django.
  Currently supported are: