Remove duplicated changelog entry (opensearch-project#7663)

Signed-off-by: Kunal Kotwani <kkotwani@amazon.com>

CHANGELOG.md

@@ -87,7 +87,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add descending order search optimization through reverse segment read. ([#7244](https://github.com/opensearch-project/OpenSearch/pull/7244))
 - Add 'unsigned_long' numeric field type ([#6237](https://github.com/opensearch-project/OpenSearch/pull/6237))
 - Add back primary shard preference for queries ([#7375](https://github.com/opensearch-project/OpenSearch/pull/7375))
-- Add descending order search optimization through reverse segment read. ([#7244](https://github.com/opensearch-project/OpenSearch/pull/7244))
 - Adds ExtensionsManager.lookupExtensionSettingsById ([#7466](https://github.com/opensearch-project/OpenSearch/pull/7466))
 - SegRep with Remote: Add hook for publishing checkpoint notifications after segment upload to remote store ([#7394](https://github.com/opensearch-project/OpenSearch/pull/7394))
 - Provide mechanism to configure XContent parsing constraints (after update to Jackson 2.15.0 and above) ([#7550](https://github.com/opensearch-project/OpenSearch/pull/7550))
@@ -136,4 +135,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Security
 
 [Unreleased 3.0]: https://github.com/opensearch-project/OpenSearch/compare/2.x...HEAD
-[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.7...2.x
+[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.7...2.x