Apply suggestion from @Alex-Welsh

Co-authored-by: Alex Welsh <112560678+Alex-Welsh@users.noreply.github.com>

Author: priteau

doc/source/operations/upgrading-openstack.rst

@@ -318,7 +318,7 @@ Then execute the migration script:
 
    After migrating to durable queues, messages are sent to all receivers, but
    only one will respond. This results in high numbers of messages staying in
-   the ready state, so the Prometheus alert RabbitMQTooMuchReady will start
+   the ready state, so the Prometheus alert ``RabbitMQTooMuchReady`` will start
    firing. This alert can be ignored, and will be removed when Prometheus is
    reconfigured.