patch 8.2.1211: removed more than dead code

Problem:    Removed more than dead code.
Solution:   Put back the decrement.
diff --git a/src/move.c b/src/move.c
index ec1ad38..767134f 100644
--- a/src/move.c
+++ b/src/move.c
@@ -2681,6 +2681,7 @@
 	    if (curwin->w_topfill > 0)
 	    {
 		i = 1;
+		--n;
 		--curwin->w_topfill;
 	    }
 	    else