fix toc link

Author: austinmccollum

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

@@ -127,7 +127,7 @@
     - name: Microsoft Fabric
       href: fabric-capacity.md
     - name: Microsoft Sentinel - Pre-Purchase
-      href: /azure/sentinel/billing-prepurchase-plan?toc=/azure/cost-management-billing/reservations/toc.json
+      href: /azure/sentinel/billing-pre-purchase-plan?toc=/azure/cost-management-billing/reservations/toc.json
     - name: SAP HANA Large Instances
       href: prepay-hana-large-instances-reserved-capacity.md
     - name: Software plans