Reduce details on message.

content/en/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions.md

@@ -763,9 +763,7 @@ The CronTab "my-new-cron-object" is invalid:
 
 The `rule` under `x-kubernetes-validations` represents the expression which will be evaluated by CEL.
 
-The `message` represents the message displayed when validation fails. The message is required if the Rule contains
-line breaks. The message must not contain line breaks. If unset, the message is "failed rule: {Rule}".
-In above example, if message is unset, the response would be:
+The `message` represents the message displayed when validation fails. If message is unset, the above response would be:
 ```
 The CronTab "my-new-cron-object" is invalid:
 * spec: Invalid value: map[string]interface {}{"maxReplicas":10, "minReplicas":0, "replicas":20}: failed rule: self.replicas <= self.maxReplicas