removed unused imports

h2/src/main/org/h2/index/BaseIndex.java

@@ -5,8 +5,6 @@
  */
 package org.h2.index;
 
-import java.util.List;
-import java.util.concurrent.Future;
 import org.h2.api.ErrorCode;
 import org.h2.engine.Constants;
 import org.h2.engine.DbObject;