[glossary] Add Zed
[glossary] Add Zed

Zed is the name for the 26th release, add it to Glossary.

Change-Id: Idf7600dbe2feeceb41b04c15faf4e4eaae5b3c59

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals