[MINOR] Suppress netty related warnings

This commit suppress the Netty related warnings
to SSL.

Closes #2121

Author: ReneEnjilian

src/main/java/org/apache/sysds/runtime/controlprogram/federated/FederatedData.java

@@ -59,6 +59,7 @@
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import io.netty.util.concurrent.Promise;
 
+@SuppressWarnings("deprecation")
 public class FederatedData {
 	private static final Log LOG = LogFactory.getLog(FederatedData.class.getName());
 	private static final Set<InetSocketAddress> _allFedSites = new HashSet<>();

src/main/java/org/apache/sysds/runtime/controlprogram/federated/FederatedWorker.java

@@ -66,6 +66,7 @@
 import io.netty.handler.codec.serialization.ObjectDecoder;
 import io.netty.handler.codec.serialization.ClassResolvers;
 
+@SuppressWarnings("deprecation")
 public class FederatedWorker {
 	protected static Logger log = Logger.getLogger(FederatedWorker.class);
 

src/main/java/org/apache/sysds/runtime/controlprogram/federated/FederationUtils.java

@@ -75,6 +75,7 @@
 import io.netty.handler.codec.serialization.ClassResolvers;
 import io.netty.handler.codec.serialization.ObjectDecoder;
 
+@SuppressWarnings("deprecation")
 public class FederationUtils {
 	protected static Logger log = Logger.getLogger(FederationUtils.class);
 	private static final IDSequence _idSeq = new IDSequence();