Remove Concurrent Segment Search feature flags for feature launch

Signed-off-by: Jay Deng <jayd0104@gmail.com>

Author: jed326

CHANGELOG.md

@@ -136,6 +136,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add `org.opensearch.rest.MethodHandlers` and `RestController#getAllHandlers` ([11876](https://github.com/opensearch-project/OpenSearch/pull/11876))
 - New DateTime format for RFC3339 compatible date fields ([#11465](https://github.com/opensearch-project/OpenSearch/pull/11465))
 - Add support for Google Application Default Credentials in repository-gcs ([#8394](https://github.com/opensearch-project/OpenSearch/pull/8394))
+- Remove concurrent segment search feature flag for GA launch ([#12074](https://github.com/opensearch-project/OpenSearch/pull/12074))
 
 ### Dependencies
 - Bumps jetty version to 9.4.52.v20230823 to fix GMS-2023-1857 ([#9822](https://github.com/opensearch-project/OpenSearch/pull/9822))

distribution/src/config/opensearch.yml

@@ -117,12 +117,6 @@ ${path.logs}
 #opensearch.experimental.feature.extensions.enabled: false
 #
 #
-# Gates the concurrent segment search feature. This feature enables concurrent segment search in a separate
-# index searcher threadpool.
-#
-#opensearch.experimental.feature.concurrent_segment_search.enabled: false
-#
-#
 # Gates the optimization of datetime formatters caching along with change in default datetime formatter
 # Once there is no observed impact on performance, this feature flag can be removed.
 #