Update doc/source/operations/upgrading-openstack.rst

Co-authored-by: Matt Anson <[email protected]>

Author: assumptionsandg

doc/source/operations/upgrading-openstack.rst

@@ -1105,7 +1105,8 @@ upgrade the Neutron API service.
 
    kayobe overcloud service upgrade --kolla-limit controllers -ke neutron_service_limit=neutron-server
 
-To ensure L3 reliability during the upgrade, we will need to manually drain
+To ensure L3 reliability during the upgrade, we will need to sequentially drain
+and upgrade each network node by first disabling agents and then running a targeted upgrade.
 the network nodes of all agents, and upgrade the nodes sequentially.
 
 Kolla credentials will need to be activated before running the neutron-namespace-drain