8198777: JList.getPreferredScrollableViewportSize(): fix mistake in doc for height calc

Reviewed-by: serb, ssadetsky

src/java.desktop/share/classes/javax/swing/JList.java

@@ -2427,7 +2427,7 @@ public class JList<E> extends JComponent implements Scrollable, Accessible
      * <p>
      * If the model isn't empty, the width is the preferred size's width,
      * typically the width of the widest list element. The height is the
-     * {@code fixedCellHeight} multiplied by the {@code visibleRowCount},
+     * height of the cell with index 0 multiplied by the {@code visibleRowCount},
      * plus the list's vertical insets.
      * <p>
      * <b>{@code VERTICAL_WRAP} or {@code HORIZONTAL_WRAP}:</b>