Feedback update to add failover REST API use case

Author: rrelledge

content/operate/rs/references/rest-api/requests/shards/actions/failover.md

@@ -22,6 +22,8 @@ weight: $weight
 
 Performs failover on the primary shards specified by `shard_uids` in the request body, and promotes their replicas to primary shards. This request is asynchronous.
 
+The cluster automatically manages failover to ensure high availability. Use this failover REST API request only for testing and planned maintenance.
+
 #### Required permissions
 
 | Permission name | Roles |
@@ -102,6 +104,8 @@ When errors are reported, the server may return a JSON object with `error_code`
 
 Performs failover on the primary shard with the specified `shard_uid`, and promotes its replica shard to a primary shard. This request is asynchronous.
 
+The cluster automatically manages failover to ensure high availability. Use this failover REST API request only for testing and planned maintenance.
+
 #### Required permissions
 
 | Permission name | Roles |