[FLINK-35134][Connectors/Elasticsearch] Change flink.version to 1.19.1

Author: reswqa

pom.xml

@@ -51,7 +51,7 @@ under the License.
 	</modules>
 
 	<properties>
-		<flink.version>1.20.0</flink.version>
+		<flink.version>1.19.1</flink.version>
 
 		<jackson-bom.version>2.15.3</jackson-bom.version>
 		<junit4.version>4.13.2</junit4.version>