8263530: sun.awt.X11.ListHelper.removeAll() should use clear()

Reviewed-by: serb, kizune

Author: shipilev

src/java.desktop/unix/classes/sun/awt/X11/ListHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -147,7 +147,7 @@ void remove(int index) {
     }
 
     void removeAll() {
-        items.removeAll(items);
+        items.clear();
         updateScrollbars();
     }