Fix alerting documentation encryption key requirement (#63512)

* Fix documentation to indicate encryption key config required regardless if security is used or not

* Update docs/user/alerting/index.asciidoc

Co-Authored-By: gchaps <33642766+gchaps@users.noreply.github.com>

* Update docs/user/alerting/index.asciidoc

Co-Authored-By: gchaps <33642766+gchaps@users.noreply.github.com>

Co-authored-by: gchaps <33642766+gchaps@users.noreply.github.com>

docs/user/alerting/index.asciidoc

@@ -154,10 +154,13 @@ Pre-packaged *alert types* simplify setup, hide the details complex domain-speci
 [[alerting-setup-prerequisites]]
 == Setup and prerequisites
 
+If you are using an *on-premises* Elastic Stack deployment:
+
+* In the kibana.yml configuration file, add the <<alert-action-settings-kb,`xpack.encryptedSavedObjects.encryptionKey`>> setting.
+
 If you are using an *on-premises* Elastic Stack deployment with <<using-kibana-with-security, *security*>>:
 
-* TLS must be configured for communication <<configuring-tls-kib-es, between {es} and {kib}>>. {kib} alerting uses <<api-keys, API keys>> to secure background alert checks and actions, and API keys require {ref}/configuring-tls.html#tls-http[TLS on the HTTP interface].
-* In the kibana.yml configuration file, add the <<alert-action-settings-kb,`xpack.encryptedSavedObjects.encryptionKey` setting>> 
+* Transport Layer Security (TLS) must be configured for communication <<configuring-tls-kib-es, between {es} and {kib}>>. {kib} alerting uses <<api-keys, API keys>> to secure background alert checks and actions, and API keys require {ref}/configuring-tls.html#tls-http[TLS on the HTTP interface].
 
 [float]
 [[alerting-security]]