Fixed activity alerts reference

Activity alerts are gone, replaced by alert policies.

Author: chrisda

defender-xdr/investigate-alerts.md

@@ -28,7 +28,7 @@ appliesto:
 [!INCLUDE [Microsoft Defender XDR rebranding](../includes/microsoft-defender.md)]
 
 > [!NOTE]
-> This article describes security alerts in Microsoft Defender XDR. However, you can use activity alerts to send email notifications to yourself or other admins when users perform specific activities in Microsoft 365. For more information, see [Create activity alerts - Microsoft Purview | Microsoft Docs](/Microsoft-365/compliance/create-activity-alerts).
+> This article describes security alerts in Microsoft Defender XDR. However, you can use alert policies to send email notifications to yourself or other admins when users perform specific activities in Microsoft 365. For more information, see [Alert policies in the Microsoft Defender portal](alert-policies.md).
 
 Alerts are the basis of all incidents and indicate the occurrence of malicious or suspicious events in your environment. Alerts are typically part of a broader attack and provide clues about an incident.
 

defender-xdr/microsoft-365-security-center-mdo.md

@@ -146,7 +146,6 @@ The **Email & collaboration** node contains features that are specific to Defend
       - [Enhanced filtering](/Exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/enhanced-filtering-for-connectors)
       - [Quarantine policies](/defender-office-365/quarantine-policies)
   - [Alert policies](alert-policies.md)
-  - [Activity alerts](/purview/create-activity-alerts)
 
 :::image type="content" source="media/mdo-m365d-nav.png" alt-text="A screenshot that shows the left navigation pane of the Defender portal focused on Email & collaboration." lightbox="media/mdo-m365d-nav.png":::