Remove mitaka release prelude note
Remove mitaka release prelude note

We had a prelude note when releasing Mitaka. This note
keep showing-up at every release while we're on Newton now.

We don't need a prelude release note, we already have nice sections
for every note we push.

This patch aims to remove this prelude starting from Newton.

Change-Id: I87cdbb2991818639967184ff35ab0b4d087db3d4

openstack/puppet-gnocchi,openstack/puppet-gnocchi