App Manager v1.124.8 release notes (#3122)

* App Manager v1.124.8 release notes

* Update rn-app-manager.md

* add version number

---------

Co-authored-by: replicated-ci-kots <[email protected]>
Co-authored-by: Ethan Mosbaugh <[email protected]>
Co-authored-by: Alex Parker <[email protected]>

Author: 4 people

docs/release-notes/rn-app-manager.md

@@ -16,7 +16,14 @@ The following table lists the versions of Kubernetes that are compatible with ea
 
 <KubernetesCompatibility/>
 
-<!--RELEASE_NOTES_PLACEHOLDER-->
+## 1.124.8
+
+Released on March 20, 2025
+
+Support for Kubernetes: 1.29, 1.30, and 1.31
+
+### Improvements {#improvements-1-124-8}
+* Updates to support custom domains for Embedded Cluster.
 
 ## 1.124.7