App Manager v1.120.3 release notes (#2813)

* App Manager v1.120.3 release notes

* Update rn-app-manager.md

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

Author: 3 people

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

@@ -18,6 +18,15 @@ The following table lists the versions of Kubernetes that are compatible with ea
 
 <!--RELEASE_NOTES_PLACEHOLDER-->
 
+## 1.120.3
+
+Released on November 7, 2024
+
+Support for Kubernetes: 1.29, 1.30, and 1.31
+
+### Improvements {#improvements-1-120-3}
+* Various updates for Embedded Cluster.
+
 ## 1.120.2
 
 Released on November 5, 2024