Add statement about defining security rules (elastic#178463)

## Summary

Pushing a commit that _should_ have been part of
elastic#177525

### Checklist

Delete any items that are not applicable to this PR.

- [x] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)

(cherry picked from commit 5e09b74)

docs/user/alerting/rule-types.asciidoc

@@ -3,7 +3,8 @@
 == Rule types
 
 A rule is a set of <<alerting-concepts-conditions, conditions>>, <<alerting-concepts-scheduling, schedules>>, and <<alerting-concepts-actions, actions>> that enable notifications. {kib} provides rules built into the {stack} and rules registered by one of the {kib} apps.
-You can create most rules types in <<create-and-manage-rules,{stack-manage-app} > {rules-ui}>>. For information on creating security rules, refer to {security-guide}/rules-ui-create.html[Create a detection rule].
+You can create most rules types in <<create-and-manage-rules,{stack-manage-app} > {rules-ui}>>.
+Security rules must be defined in the Security app. For more information, refer to the documentation about {security-guide}/rules-ui-create.html[creating a detection rule].
 
 [NOTE]
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