Modify change log

Signed-off-by: Gao Binlong <[email protected]>

Author: gaobinlong

CHANGELOG.md

@@ -80,7 +80,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix indexing error when flat_object field is explicitly null ([#15375](https://github.com/opensearch-project/OpenSearch/pull/15375))
 - Fix split response processor not included in allowlist ([#15393](https://github.com/opensearch-project/OpenSearch/pull/15393))
 - Fix unchecked cast in dynamic action map getter ([#15394](https://github.com/opensearch-project/OpenSearch/pull/15394))
-- Fix updating search backpressure settings crashing the cluster
+- Add validation for the search backpressure cancellation settings ([#15501](https://github.com/opensearch-project/OpenSearch/pull/15501))
 
 ### Security