docs: update release note for 1.31 now that it is released

docs/releases/1.31-NOTES.md

@@ -1,30 +1,16 @@
 ## Release notes for kOps 1.31 series
 
-**⚠ kOps 1.30 has not been released yet! ⚠**
-
 This is a document to gather the release notes prior to the release.
 
 # Significant changes
 
-* **Kubernetes minor version upgrades to 1.31 *must* be performed using a new `kops reconcile cluster` command.**
-
-  See [docs/tutorial/upgrading-kubernetes.md](/docs/tutorial/upgrading-kubernetes.md) for more details.
-
-## Some Feature
-
-Lorem ipsum....
-
-## AWS
-
-* TODO
+* **Kubernetes minor version upgrades to 1.31 *should* be performed using a new `kops reconcile cluster` command.**
 
-## GCP
+  Kubernetes 1.31 introduces stricter checks around the version-skew policy. While kOps has always followed the
+  version-skew policy, there was an edge case: nodes that were added by an autoscaler during a rolling-update
+  would not always follow the version-skew policy.
 
-* TODO
-
-## Openstack
-
-* TODO
+  See [docs/tutorial/upgrading-kubernetes.md](/docs/tutorial/upgrading-kubernetes.md) for more details.
 
 # Other changes of note
 
@@ -33,15 +19,6 @@ Lorem ipsum....
 * Spotinst cluster controller V1 is replaced with Ocean kubernetes controller V2, all old k8s resource are removed
   except spotinst-kubernetes-cluster-controller Secret.
 
-# Breaking changes
-
-## Other breaking changes
-
-* TODO
-
-# Known Issues
-
-* TODO
 
 # Deprecations