Remove unused method.

h2/src/test/org/h2/samples/ShowProgress.java

@@ -86,13 +86,6 @@ public class ShowProgress implements DatabaseEventListener {
 
     }
 
-    /**
-     * This method is called by the database if disk space is low.
-     */
-    public void diskSpaceIsLow() {
-        System.out.println("diskSpaceIsLow");
-    }
-
     /**
      * This method is called if an exception occurs in the database.
      *