anchor.diff:  This has been renamed to `kibana_system` in order to reduce confusion, and to better
   align with other built-in system accounts.
   
  +*Impact* +
  +Replace any use of the `kibana` user with the `kibana_system` user. Specifying
  +the `kibana` user in `kibana.yml` will result in an error on startup.
  +
   If your `kibana.yml` used to contain:
   [source,yaml]
   --------------------------------------------------
  
positive.code: *Details* +
  The `xpack.security.authc.realms.{type}.{name}.order` setting is now required and must be
  specified for each explicitly configured realm. Each value must be unique.
  The cluster will fail to start if the requirements are not met.
  
  For example, the following configuration is invalid:
  
negative.code: The `transport.profiles.*.xpack.security.type` setting has been removed since
  the Transport Client has been removed and therefore all client traffic now uses
  the HTTP transport. Transport profiles using this setting should be removed.
  
  *Impact* +
  Discontinue use of the `transport.profiles.*.xpack.security.type` setting.
  Specifying this setting in a transport profile in `elasticsearch.yml` will
  result in an error on startup.
  ====
  
  [discrete]
  