[MINOR] Fix unnecessary warnings (code quality)

Author: mboehm7

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

@@ -29,8 +29,6 @@
 import java.util.Set;
 import java.util.concurrent.Future;
 
-import javax.net.ssl.SSLException;
-
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;

src/main/java/org/apache/sysds/runtime/frame/data/lib/FrameUtil.java

@@ -19,8 +19,6 @@
 
 package org.apache.sysds.runtime.frame.data.lib;
 
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.regex.Pattern;
 
 import org.apache.commons.logging.Log;
@@ -35,8 +33,6 @@
 import org.apache.sysds.runtime.frame.data.columns.FloatArray;
 import org.apache.sysds.runtime.frame.data.columns.IntegerArray;
 import org.apache.sysds.runtime.frame.data.columns.LongArray;
-import org.apache.sysds.runtime.frame.data.iterators.IteratorFactory;
-import org.apache.sysds.runtime.util.UtilFunctions;
 
 public interface FrameUtil {
 	public static final Log LOG = LogFactory.getLog(FrameUtil.class.getName());