[doc] point release note docs to project team guide
[doc] point release note docs to project team guide

no point in maintaining our own doc, the project team guide
(not to be confused with the other PTG) already documents
when and how to create release notes.

Change-Id: I894b335fbb1d4b16d1813c11c9dc912dcbf55bba

mahak/keystone,mahak/keystone,openstack/keystone,openstack/keystone,rajalokan/keystone,mahak/keystone,openstack/keystone,ilay09/keystone,rajalokan/keystone,ilay09/keystone,ilay09/keystone,rajalokan/keystone