message: docs: update example to accurately reflect description
diff: @@ -285,7 +285,7 @@ Example 5: Envoy as an internal proxy, receiving a request from an internal clie
  Result:
  | Trusted client address = 10.20.30.40
  | X-Envoy-External-Address remains unset
  - | X-Envoy-Internal is set to "true"
  + | X-Envoy-Internal is set to "false"
  Example 6: The internal Envoy from Example 5, receiving a request proxied by another Envoy
  Settings:
  