patch 8.2.0523: loops are repeated

Problem:    Loops are repeated.
Solution:   Use FOR_ALL_ macros. (Yegappan Lakshmanan, closes #5882)
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 0dfe5a1..359007a 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -3984,7 +3984,7 @@
 	l = heredoc_get(eap, op + 3);
 
 	// Push each line and the create the list.
-	for (li = l->lv_first; li != NULL; li = li->li_next)
+	FOR_ALL_LIST_ITEMS(l, li)
 	{
 	    generate_PUSHS(cctx, li->li_tv.vval.v_string);
 	    li->li_tv.vval.v_string = NULL;