Revert "Merge pull request #26053 from qarmin/back_scroll_to_start"

This reverts commit b5deb1dc72d8c4c92c9850379522926e60ddf7d0, reversing
changes made to 2cc8848c3c3815c6f72ce5f9b75bfab8a1498292.

This change causes unwanted regression.
It's too risky to have scroll back to top in ItemList.clear()

scene/gui/item_list.cpp

@@ -369,7 +369,6 @@ void ItemList::clear() {
 	update();
 	shape_changed = true;
 	defer_select_single = -1;
-	scroll_bar->set_value(0);
 }
 
 void ItemList::set_fixed_column_width(int p_size) {