With the new release identification / naming schema [1] (like:
2023.1 Antelope) new stable branch naming was introduced (like:
stable/2023.1). list_rc_updates.sh script was not updated to this
new branch naming.
[1] https://governance.openstack.org/tc/reference/release-naming.html
Change-Id: If7027d462324d705e18c4a579316175a700e0548