patch 9.1.0100: Redrawing can be improved with undo and 'spell'

Problem:  When undoing with 'spell', redrawWinline() is called after
          changed_lines(), while later win_update() sets redraw type to
          UPD_NOT_VALID, even though w_redraw_top and w_redraw_bot are
          still valid.
Solution: Only set redraw type to UPD_NOT_VALID when inserting/deleting
          lines after parts of window has pending redraw, i.e., when
          changed_lines() is called after redrawWinline().
          (zeertzjq)

closes: #14019

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/popupwin.c b/src/popupwin.c
index 64bb0b5..bdf4ac7 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -3899,8 +3899,8 @@
 
 			// The screen position "line" / "col" needs to be
 			// redrawn.  Figure out what window that is and update
-			// w_redraw_top and w_redr_bot.  Only needs to be done
-			// once for each window line.
+			// w_redraw_top and w_redraw_bot.  Only needs to be
+			// done once for each window line.
 			wp = mouse_find_win(&line_cp, &col_cp, IGNORE_POPUP);
 			if (wp != NULL)
 			{