(DOCSP-49628) Add SASL_SSL mention to VPC peering docs (#14480)

* (DOCSP-49628) Add SASL_SSL mention to VPC peering docs

* (DOCSP-49628) Formatting fix

Author: lmkerbey-mdb

content/atlas/source/atlas-stream-processing/manage-vpc-peering-connections.txt

@@ -78,14 +78,21 @@ To create outbound |vpc| peering connections to your {+spi+}:
       to your cloud provider |vpc| using the {+atlas-ui+}, 
       see :ref:`Add an Atlas Stream Processing Connection
       <atlas-sp-add-connection>` and select :guilabel:`Apache Kafka`
-      as your connection type, and :guilabel:`Atlas UI` as your interface.
+      as your connection type, and :guilabel:`Atlas UI` as your
+      interface.
+
+      You must select ``SASL_SSL`` as your security protocol for VPC
+      peering connections.
 
    .. tab:: {+atlas-admin-api+}
       :tabid: api
 
       To create outbound |vpc| peering connections to your {+spi+} using the API, see 
       :oas-atlas-tag:`Return All Network Peering Connections in One Project </Network-Peering/operation/listPeeringConnections>`.
 
+      You must select ``SASL_SSL`` as your security protocol for VPC
+      peering connections.      
+
 .. _generate-incoming-vpc-peering-connection-from-confluent:
 .. _atlas-sp-generate-incoming-vpc-peering-connection-from-confluent: