disclaimer - alerts are displayed even if the impacted resource was deleted

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cc: @bmansheim

Author: berlihie

articles/defender-for-cloud/alerts-overview.md

@@ -18,6 +18,8 @@ Security alerts are the notifications generated by Defender for Cloud and Defend
 - Each alert provides details of affected resources, issues, and remediation recommendations.
 - Defender for Cloud classifies alerts and prioritizes them by severity in the Defender for Cloud portal.
 - Alerts data is retained for 90 days.
+- An alert that was triggered on a resource will continue to be displayed for 90 days even if the resource was deleted during that time. This is because the alert
+  might indicate a potential breach to your organization that needs to be further investigated.     
 - Alerts can be exported to CSV format, or directly injected into Microsoft Sentinel.
 - Defender for Cloud leverages the [MITRE Attack Matrix](https://attack.mitre.org/matrices/enterprise/) to associate alerts with their perceived intent, helping formalize security domain knowledge.