fsmonitor: mark unused hashmap callback parameters

Like many hashmap comparison functions, our cookies_cmp() does not look
at its extra void data parameter. This should have been annotated in
02c3c59 (hashmap: mark unused callback parameters, 2022-08-19), but
this new case was added around the same time (plus fsmonitor is not
built at all on Linux, so it is easy to miss there).

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

builtin/fsmonitor--daemon.c

@@ -129,8 +129,9 @@ struct fsmonitor_cookie_item {
  enum fsmonitor_cookie_item_result result;
 };
 
-static int cookies_cmp(const void *data, const struct hashmap_entry *he1,
- const struct hashmap_entry *he2, const void *keydata)
+static int cookies_cmp(const void *data UNUSED,
+ const struct hashmap_entry *he1,
+ const struct hashmap_entry *he2, const void *keydata)
 {
  const struct fsmonitor_cookie_item *a =
  container_of(he1, const struct fsmonitor_cookie_item, entry);