Adds Serverless badge to Configure data volume for Elastic Endpoint page (#1074)

Contributes to elastic/security-docs#5771.

Adds Serverless applies tag to the Configure data volume for Elastic
Endpoint page. Confirmed with Dan Ferullo that this change is being
released in Serverless at the same time 8.18 is released.

Preview: [Configure data
volume](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/1074/solutions/security/configure-elastic-defend/configure-data-volume-for-elastic-endpoint)

Author: natasha-moore-elastic

solutions/security/configure-elastic-defend/configure-data-volume-for-elastic-endpoint.md

@@ -5,6 +5,8 @@ mapped_pages:
   - https://www.elastic.co/guide/en/serverless/current/security-endpoint-data-volume.html
 applies_to:
   stack: all
+  serverless:
+    security: all
 ---
 
 # Configure data volume for {{elastic-endpoint}} [endpoint-data-volume]