update prompt

Author: m-chau

src/aks-preview/azext_aks_preview/custom.py

@@ -1260,8 +1260,10 @@ def aks_upgrade(cmd,
             upgrade_all = True
         else:
             msg = (
-                "Since control-plane-only argument is specified, this will upgrade only the control plane to "
-                f"{instance.kubernetes_version}. Node pool will not change. Continue?"
+                "Since control-plane-only argument is specified, this will upgrade only the kubernetes version of the control plane to  "
+                f"{instance.kubernetes_version}. Kubernetes versions of the node pools will remain unchanged, "
+                "but node image version may be upgraded if there has been cluster config change that requires VM reimage. "
+                "Continue?"
             )
             if not yes and not prompt_y_n(msg, default="n"):
                 return None