End support for stable/2023.2

Stable/2023.2 is EOL now[1] and Tempest
does not support EOL releases so this marks
the end of support for stable/2023.2.

This adds the release note to mark the end of
support of 2023.2 as well as drop the job.

[1] https://review.opendev.org/c/openstack/releases/+/948580

Change-Id: I79959d34c82498b389cb4ba9e72a8b71b74c191a
4 files changed