standardize release note page ordering

In order to support automatically updating the release notes when we
create stable branches, we want the pages to be in a standard order.
This patch updates the order to be reverse chronological, so the most
recent notes appear at the top.

Change-Id: Ib364dcc8eb31275a31c83b68d7914263b183e393
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

Author: dhellmann

releasenotes/source/index.rst

@@ -6,9 +6,9 @@ OpenStackClient Release Notes
    :maxdepth: 1
 
    unreleased
+   newton
    20_releases
    pre_20_releases
-   newton
 
 OpenStack Releases
 ------------------