patch 8.2.5107: some callers of rettv_list_alloc() check for not OK

Problem:    Some callers of rettv_list_alloc() check for not OK. (Christ van
            Willegen)
Solution:   Use "==" instead of "!=" when checking the return value.
diff --git a/src/list.c b/src/list.c
index b9a3478..10a7aac 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1762,7 +1762,7 @@
     }
 
     vimlist_remove(l, item, item2);
-    if (rettv_list_alloc(rettv) != OK)
+    if (rettv_list_alloc(rettv) == FAIL)
 	return;
 
     rl = rettv->vval.v_list;