reftable: mark unused parameters in empty iterator functions

These unused parameters were marked in a68ec86 (reftable: mark unused
parameters in virtual functions, 2024-08-17), but the functions were
moved to a new file in a parallel branch via f2406c8
(reftable/generic: move generic iterator code into iterator interface,
2024-08-22).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: peff

reftable/iter.c

@@ -25,17 +25,17 @@ int iterator_next(struct reftable_iterator *it, struct reftable_record *rec)
 	return it->ops->next(it->iter_arg, rec);
 }
 
-static int empty_iterator_seek(void *arg, struct reftable_record *want)
+static int empty_iterator_seek(void *arg UNUSED, struct reftable_record *want UNUSED)
 {
 	return 0;
 }
 
-static int empty_iterator_next(void *arg, struct reftable_record *rec)
+static int empty_iterator_next(void *arg UNUSED, struct reftable_record *rec UNUSED)
 {
 	return 1;
 }
 
-static void empty_iterator_close(void *arg)
+static void empty_iterator_close(void *arg UNUSED)
 {
 }