Mention switch from extras to extras common

Author: jovial

releasenotes/notes/bump-centos8-stream-snapshots-2023-09-04-a473edfd3f3b2298.yaml

@@ -12,3 +12,8 @@ upgrade:
     must be reconfigured to exclude a `buggy version of iptables
     <https://bugzilla.redhat.com/show_bug.cgi?id=2236501>`__. To do this use:
     ``kayobe overcloud service reconfigure -kt none -t dnf``.
+  - |
+    CentOS Extras has been replaced with CentOS Extras Common. You may need to
+    use the ``--allowerasing`` option with DNF if you have packages installed
+    from the old repo. This is a one time only thing and on the next package
+    update you can drop this argument.