Update master for stable/2023.2

Add file to the reno documentation build to show release notes for
stable/2023.2.

Use pbr instruction to increment the minor version number
automatically so that master versions are higher than the versions on
stable/2023.2.

Sem-Ver: feature
Change-Id: I96140b1e3be06b60909f3eed739f1a944e119c7e

releasenotes/source/2023.2.rst

+===========================
+2023.2 Series Release Notes
+===========================
+
+.. release-notes::
+   :branch: stable/2023.2

releasenotes/source/index.rst

@@ -8,6 +8,7 @@ Contents
    :maxdepth: 2
 
    unreleased
+   2023.2
    2023.1
    zed
    yoga