Docs: Update vip failover commands

It is best practice to use systemctl to stop and start containers.

Author: jovial

doc/source/operations/ubuntu-noble.rst

@@ -153,8 +153,8 @@ long enough).
 
 .. code-block:: bash
 
-   sudo docker stop keepalived
-   sudo docker start keepalived
+   sudo sudo systemctl stop kolla-keepalived-container.service
+   sudo sudo systemctl start kolla-keepalived-container.service
 
 Always back up the overcloud DB before starting: