Remove "AlmanacPropertyInterface" from "AlmanacNamespace"

Summary:
See https://discourse.phabricator-community.org/t/i-cant-create-almanac-space/4424/.

Almanac namespaces have never really had property support, but they implemented the interface in the original implementation.

At the time, this had no effect. Later changes integrated properties into the edit flows and broke this no-op integration.

Remove the interface for now. They could be given property support later, but need a bit of support code.

This feature is very rarely used and primarily useful for Phacility instances.

Test Plan: Created new namespaces and edited namespaces, browsed namespace UI.

Differential Revision: https://secure.phabricator.com/D21543