Add tutorial to TOC

Author: cwatson-cat

articles/sentinel/TOC.yml

@@ -15,6 +15,8 @@
   items:
   - name: Forward syslog data to workspace
     href: forward-syslog-monitor-agent.md
+  - name: Configure a data retention policy
+    href: configure-data-retention.md
   - name: Investigate with UEBA
     href: investigate-with-ueba.md
   - name: Use automation to respond to threats