Update master for stable/2026.2

Add file to the reno documentation build to show release notes for
stable/2026.2.

Use pbr instruction to increment the minor version number
automatically so that master versions are higher than the versions on
stable/2026.2.

Sem-Ver: feature
Change-Id: I66d190065a6062ac57903bd9296182c897c18b03
Signed-off-by: OpenStack Release Bot <infra-root@openstack.org>
Generated-By: openstack/project-config:roles/copy-release-tools-scripts/files/release-tools/add_release_note_page.sh

releasenotes/source/2026.2.rst

@@ -0,0 +1,6 @@
+===========================
+2026.2 Series Release Notes
+===========================
+
+.. release-notes::
+   :branch: stable/2026.2

releasenotes/source/index.rst

@@ -5,6 +5,7 @@ oslo.upgradecheck Release Notes
    :maxdepth: 1
 
    unreleased
+   2026.2
    2026.1
    2025.2
    2025.1