Make warning more clear

Co-authored-by: Alex Welsh <[email protected]>

Author: seunghun1ee

doc/source/operations/upgrading-openstack.rst

@@ -289,14 +289,18 @@ must be migrated to Ubuntu 24.04 before upgrading OpenStack services.
 You can find the upgrade procedure from :ref:`upgrading-to-ubuntu-noble`
 documentation.
 
-RabbitMQ 4.1
-------------
+
+RabbitMQ Prerequisites
+----------------------
 
 .. warning::
 
    StackHPC Kayobe Config sets RabbitMQ 4.1 as the default for the Epoxy release.
    Existing transient queues must be migrated to durable queues with Queue Manager
    before upgrading to RabbitMQ 4.1.
+   
+   This means that queue migration and the RabbitMQ 4.1 upgrade must be completed
+   before upgrading to Epoxy.
 
 Queue Migration
 ~~~~~~~~~~~~~~~