Add to CHANGELOG

Signed-off-by: Craig Perkins <cwperx@amazon.com>

Author: cwperks

CHANGELOG.md

@@ -42,6 +42,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix potential concurrent modification exception when updating allocation filters ([#19701])(https://github.com/opensearch-project/OpenSearch/pull/19701))
 - Fix file-based ingestion consumer to handle start point beyond max line number([#19757])(https://github.com/opensearch-project/OpenSearch/pull/19757))
 - Fixed assertion unsafe use of ClusterService.state() in ResourceUsageCollectorService ([#19775])(https://github.com/opensearch-project/OpenSearch/pull/19775))
+- Add S3Repository.LEGACY_MD5_CHECKSUM_CALCULATION to list of repository-s3 settings ([#19788](https://github.com/opensearch-project/OpenSearch/pull/19788))
 
 ### Dependencies
 - Update to Gradle 9.1 ([#19575](https://github.com/opensearch-project/OpenSearch/pull/19575))