[7.10] [DOCS] Adds missing monitoring.cluster_alerts.email_notifications.enabled setting (elastic#127323) (elastic#127389)

* [DOCS] Adds missing `monitoring.cluster_alerts.email_notifications.enabled` setting (elastic#127323)

* [DOCS] Adds missing  setting

* Removes deprecation message for unsupported version

(cherry picked from commit 27b5735)

* Removes rogue ::

Co-authored-by: Spencer <[email protected]>

Author: KOTungseth

docs/settings/monitoring-settings.asciidoc

@@ -31,6 +31,9 @@ For more information, see
 
 [cols="2*<"]
 |===
+| `monitoring.cluster_alerts.email_notifications.enabled`
+  | When enabled, sends email notifications for Watcher alerts to the specified email address. The default is `true`. 
+
 | `monitoring.cluster_alerts.email_notifications.email_address` {ess-icon}::
   | When enabled, specifies the email address where you want to receive cluster alert notifications.