[AKS] Fix #2457: Clarify subnet id description to resource id (#23234)

Fixes Azure/azure-cli-extensions#2457

Author: RakeshMohanMSFT

src/azure-cli/azure/cli/command_modules/acs/_help.py

@@ -987,10 +987,10 @@
     short-summary: Public IP prefix ID used to assign public IPs to VMSS nodes.
   - name: --vnet-subnet-id
     type: string
-    short-summary: The ID of a subnet in an existing VNet into which to deploy the cluster.
+    short-summary: The Resource Id of a subnet in an existing VNet into which to deploy the cluster.
   - name: --pod-subnet-id
     type: string
-    short-summary: The ID of a subnet in an existing VNet into which to assign pods in the cluster (requires azure network-plugin).
+    short-summary: The Resource Id of a subnet in an existing VNet into which to assign pods in the cluster (requires azure network-plugin).
   - name: --ppg
     type: string
     short-summary: The ID of a PPG.