patch 8.2.3688: the window title is not updated when dragging the scrollbar

Problem:    The window title is not updated when dragging the scrollbar.
Solution:   Call maketitle(). (Christian Brabandt, closes #9238, closes #5383)

src/gui.c

@@ -4412,6 +4412,10 @@ gui_update_scrollbars(
 					    val, size, max);
 	}
     }
+
+    // update the title, it may show the scroll position
+    maketitle();
+
     prev_curwin = curwin;
     --hold_gui_events;
 }