Remove unused permitted_instance_types
Remove unused permitted_instance_types

Commit 5ea7db9b removed the ArchFilter and moved its functionality
to the ImagePropertiesFilter, which uses 'supported_instances' from
the compute nodes to determine if a node satisfies the arch,
preferred hypervisor, and virtual machine mode requested by the
instance.  permitted_instance_types is no longer used and can be
removed.

Change-Id: Idf9d72746d7c3dcd2a7385913823df122eaa7cd6

openstack/oslo.versionedobjects,citrix-openstack-build/oslo.versionedobjects