Explain why Agent needs to connect to Kibana (#1627) (#1629)

* Explain why Agent needs to connect to Kibana

* Update docs/en/ingest-management/fleet/add-fleet-server-on-prem.asciidoc

---------

Co-authored-by: David Kilfoyle <[email protected]>
(cherry picked from commit bac20b6)

Co-authored-by: nima <[email protected]>

Author: mergify[bot]

docs/en/ingest-management/fleet/add-fleet-server-on-prem.asciidoc

@@ -98,6 +98,9 @@ You may need to allow access to these ports. Refer to the following table for de
 | {fleet-server} → {es} | 9200
 |===
 
+NOTE: Connectivity to {kib} on port 5601 is optional and not required at all times. {agent} and {fleet-server} may need to connect to {kib} if deployed in a 
+container environment where an enrollment token can not be provided during deployment. 
+
 //[discrete]
 //[[add-fleet-server-on-prem-hosts]]
 //= Add {fleet-server} hosts