Add support for ES 9.0

Author: henrikno

v2/elasticsearch-common/src/main/java/com/google/cloud/teleport/v2/elasticsearch/utils/ElasticsearchIO.java

@@ -1666,10 +1666,11 @@ static int getBackendVersion(ConnectionConfiguration connectionConfiguration) {
               || backendVersion == 5
               || backendVersion == 6
               || backendVersion == 7
-              || backendVersion == 8),
+              || backendVersion == 8
+              || backendVersion == 9),
           "The Elasticsearch version to connect to is %s.x. "
               + "This version of the ElasticsearchIO is only compatible with "
-              + "Elasticsearch v8.x, v7.x, v6.x, v5.x and v2.x",
+              + "Elasticsearch v9.x, v8.x, v7.x, v6.x, v5.x and v2.x",
           backendVersion);
       return backendVersion;