DOCS: address review comments for PR #30959

- Clarify network_plugin upgrade from kubenet to azure requires overlay mode
- Update pod_cidr/pod_cidrs to say 'Changing or removing a non-empty value'

Author: ms-henglu

website/docs/r/kubernetes_cluster.html.markdown

@@ -658,7 +658,7 @@ A `microsoft_defender` block supports the following:
 
 A `network_profile` block supports the following:
 
-* `network_plugin` - (Required) Network plugin to use for networking. Currently supported values are `azure`, `kubenet` and `none`. Changing this forces a new resource to be created, except when upgrading from `kubenet` to `azure`.
+* `network_plugin` - (Required) Network plugin to use for networking. Currently supported values are `azure`, `kubenet` and `none`. Changing this forces a new resource to be created, except when upgrading from `kubenet` to `azure` with `network_plugin_mode` set to `overlay`.
 
 ~> **Note:** When `network_plugin` is set to `azure` - the `pod_cidr` field must not be set, unless specifying `network_plugin_mode` to `overlay`.
 
@@ -694,9 +694,9 @@ A `network_profile` block supports the following:
 
 -> **Note:** For more information on supported `outbound_type` migration paths please see the product [documentation](https://learn.microsoft.com/azure/aks/egress-outboundtype#updating-outboundtype-after-cluster-creation).
 
-* `pod_cidr` - (Optional) The CIDR to use for pod IP addresses. This field can only be set when `network_plugin` is set to `kubenet` or `network_plugin_mode` is set to `overlay`. Changing a non-empty value forces a new resource to be created.
+* `pod_cidr` - (Optional) The CIDR to use for pod IP addresses. This field can only be set when `network_plugin` is set to `kubenet` or `network_plugin_mode` is set to `overlay`. Changing or removing a non-empty value forces a new resource to be created.
 
-* `pod_cidrs` - (Optional) A list of CIDRs to use for pod IP addresses. For single-stack networking a single IPv4 CIDR is expected. For dual-stack networking an IPv4 and IPv6 CIDR are expected. Changing a non-empty value forces a new resource to be created.
+* `pod_cidrs` - (Optional) A list of CIDRs to use for pod IP addresses. For single-stack networking a single IPv4 CIDR is expected. For dual-stack networking an IPv4 and IPv6 CIDR are expected. Changing or removing a non-empty value forces a new resource to be created.
 
 * `service_cidr` - (Optional) The Network Range used by the Kubernetes service. Changing this forces a new resource to be created.