[FLINK-15868] Pin snakeyaml dependency in flink-connector-elasticsear…

…ch5 to 1.25

This closes #11006.

flink-connectors/flink-connector-elasticsearch5/pom.xml

@@ -40,6 +40,17 @@ under the License.
 		<elasticsearch.version>5.1.2</elasticsearch.version>
 	</properties>
 
+	<dependencyManagement>
+		<dependencies>
+			<!-- Bump version to 1.25 to make it work with Jackson dependencies (2.10.1) -->
+			<dependency>
+				<groupId>org.yaml</groupId>
+				<artifactId>snakeyaml</artifactId>
+				<version>1.25</version>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
+
 	<dependencies>
 
 		<!-- core dependencies -->