feat: add warning about limitations of kosmos upgrade (#3857)

Author: pierreozoux

containers/kubernetes/how-to/edit-kosmos-cluster.mdx

@@ -104,6 +104,10 @@ In order to add external nodes to your multi-cloud cluster, you must first [crea
 
 ## How to upgrade nodes in a multi-cloud pool in your Kosmos cluster
 
+<Message type="important">
+  Note that the node will reappear with a different node ID. If your automation uses this ID (for instance when you use local PVCs), it will be broken.
+</Message>
+
 The Kubernetes version of the existing nodes in your multi-cloud pool can be upgraded in place. Your workload will theoretically keep running during the upgrade, but it is best to drain the node before the upgrade.
 
 1. In the Pools section of your Kosmos cluster, click **Upgrade** next to the node pool. This will not cause any of your existing nodes to upgrade, but will instead ensure that any new nodes added to the pool will start up with the newer version.