{AKS} az aks nodepool upgrade: Fix the wrong prompt when specifying…

… the `--kubernetes-version` (#29638)

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

@@ -2473,7 +2473,7 @@ def aks_agentpool_upgrade(cmd, client, resource_group_name, cluster_name,
 
     instance = client.get(resource_group_name, cluster_name, nodepool_name)
 
-    if kubernetes_version != '' or instance.orchestrator_version == kubernetes_version:
+    if kubernetes_version == '' or instance.orchestrator_version == kubernetes_version:
         msg = "The new kubernetes version is the same as the current kubernetes version."
         if instance.provisioning_state == "Succeeded":
             msg = "The cluster is already on version {} and is not in a failed state. No operations will occur when upgrading to the same version if the cluster is not in a failed state.".format(instance.orchestrator_version)