Merge pull request #6852 from k8s-infra-cherrypick-robot/cherry-pick-…

…6830-to-release-1.2

[release-1.2] 📖 add disclaimer about clusterctl topology dryrun RuntimeSDK support

docs/book/src/clusterctl/commands/alpha-topology-plan.md

@@ -24,7 +24,7 @@ the input should have all the objects needed.
 
 <aside class="note">
 
-<h1>Limitations</h1>
+<h1>Limitations: Server Side Apply</h1>
 
 The topology controllers uses [Server Side Apply](https://kubernetes.io/docs/reference/using-api/server-side-apply/)
 to support use cases where other controllers are co-authoring the same objects, but this kind of interactions can't be recreated
@@ -43,6 +43,14 @@ More specifically:
 
 </aside>
 
+<aside class="note">
+
+<h1>Limitations: RuntimeSDK</h1>
+
+Please note that `clusterctl` doesn't support Runtime SDK yet. This means that ClusterClasses with external patches are not yet supported.
+
+</aside>
+
 ## Example use cases
 
 ### Designing a new ClusterClass