Update documentation for release tasks

Since Kayobe is now an official OpenStack deliverable, our releases
documentation page is now outdated. It needs to be updated to document
the process using official release tools.

This change makes the releases page more similar to the Kolla release
management page:
https://docs.openstack.org/kolla/latest/contributor/release-management.html.

Change-Id: Ic49a63d66dfdb8e4235a60c1f01ad70bef6bea43
Story: 2007079
Task: 37990