Update dependency org.opensearch.client:opensearch-java to v2.20.0 (#66)

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build.gradle

@@ -21,9 +21,9 @@ buildscript {
             opensearch_build += "-SNAPSHOT"
         }
 
-        opensearch_java_version = '2.19.0'
         apache_http_components_version = '5.4.1'
         apache_http_core_version = '5.3.2'
+        opensearch_java_version = '2.20.0'
         aws_sdk_version = '2.29.50'
         junit_version = '5.11.4' // version catalog is 4.x
     }