remove unused imports (#3032)

* del unused imports

* del unused imports

core/src/main/java/hudson/WebAppMain.java

@@ -31,7 +31,6 @@ import java.nio.file.StandardOpenOption;
 import jenkins.util.SystemProperties;
 import com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider;
 import com.thoughtworks.xstream.core.JVM;
-import com.trilead.ssh2.util.IOUtils;
 import hudson.model.Hudson;
 import hudson.security.ACL;
 import hudson.util.BootFailure;
@@ -62,7 +61,6 @@ import javax.servlet.ServletResponse;
 import javax.xml.transform.TransformerFactory;
 import javax.xml.transform.TransformerFactoryConfigurationError;
 import java.io.File;
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.net.URL;
 import java.net.URLClassLoader;