Add IOC Device Update to tree

docs-ref-mapping/reference-unified.yml

@@ -540,6 +540,11 @@
       - com.microsoft.azure.sdk.iot*
       - com.microsoft.connecteddevices*
       - tools.com.microsoft.azure.sdk.iot*
+    - name: Device Update
+      uid: azure.java.sdk.landingpage.services.iot.deviceupdate
+      landingPageType: Service
+      children:
+      - com.azure.iot.deviceupdate*
   - name: Key Vault
     uid: azure.java.sdk.landingpage.services.keyvault
     href: ~/docs-ref-services/{moniker}/keyvault.md