Bump org.opensearch.client:opensearch-rest-high-level-client

Bumps [org.opensearch.client:opensearch-rest-high-level-client](https://github.com/opensearch-project/OpenSearch) from 2.16.0 to 2.18.0.
- [Release notes](https://github.com/opensearch-project/OpenSearch/releases)
- [Changelog](https://github.com/opensearch-project/OpenSearch/blob/main/CHANGELOG.md)
- [Commits](opensearch-project/OpenSearch@2.16.0...2.18.0)

---
updated-dependencies:
- dependency-name: org.opensearch.client:opensearch-rest-high-level-client
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

build.gradle

@@ -134,7 +134,7 @@ ext {
     kafkaVersion = "3.5.0"
     apacheCommonsLangVersion = "3.17.0"
     slf4jVersion = "1.7.36"
-    openSearchVersion = "2.16.0"
+    openSearchVersion = "2.18.0"
 
     testcontainersVersion = "1.20.3"
 }