Remove unused imports

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@272639 13f79535-47bb-0310-9956-ffa450edef68

proposal/mutant/src/java/antlibs/system/org/apache/ant/antlib/system/Ref.java

@@ -53,10 +53,8 @@
  */
 package org.apache.ant.antlib.system;
 import java.io.File;
-import org.apache.ant.common.antlib.AbstractTask;
 import org.apache.ant.common.antlib.AntContext;
 import org.apache.ant.common.model.Project;
-import org.apache.ant.common.service.ExecService;
 import org.apache.ant.common.util.ExecutionException;
 
 /**