Update TOC.yml

Author: mimckitt

articles/virtual-machine-scale-sets/TOC.yml

@@ -99,6 +99,8 @@
   - name: vCPU quotas
     href: ../virtual-machines/linux/quotas.md
     maintainContext: true
+  - name: Availability Zones
+    href: virtual-machine-scale-sets-use-availability-zones.md
   - name: Capacity reservations
     href: ../virtual-machines/capacity-reservation-overview.md
   - name: Automatic instance repairs