Update TOC.yml

Author: denisebmsft

defender-vulnerability-management/TOC.yml

@@ -42,6 +42,8 @@
             href: tvm-hardware-and-firmware.md
       - name: Authenticated scan for Windows
         href: windows-authenticated-scan.md
+      - name: Understand retention logic 
+        href: retention-logic-mdvm.md
     - name: Detect and assess threats
       items:
       - name: Dashboard insights