Update toc.yml

Author: JasonWHowell

articles/cost-management-billing/reservations/toc.yml

@@ -44,7 +44,8 @@
     - name: Dedicated Hosts
       href: billing-understand-dedicated-hosts-reservation-charges.md
     - name: Defender for Cloud - Prepurchase
-      href: ../../defender-for-cloud/prepurchase-plan.md?toc=/azure/cost-management-billing/reservations/toc.json
+      href: /azure/defender-for-cloud/prepurchase-plan
+      maintainContext: true
     - name: Disk Storage
       href: understand-disk-reservations.md
     - name: Red Hat Linux Enterprise