nat_transversal: fix warning introduced at f301ca9cdcc044dd05e9d82139e1db368be6dc5c

> nat_traversal.c: In function 'get_register_expire':
> ../../core/parser/../dprint.h:321:73: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 11 has type 'long unsigned int' [-Wformat=]
>   321 |                                                         fprintf(stderr, "%2d(%d) %s: %.*s%s%s%s" fmt, \
>       |                                                                         ^~~~~~~~~~~~~~~~~~~~~~~~

src/modules/nat_traversal/nat_traversal.c

@@ -923,7 +923,7 @@ static time_t get_register_expire(
 		}
 	}
 
-	LM_DBG("maximum expire for all contacts: %llu\n", (uint64_t)expire);
+	LM_DBG("maximum expire for all contacts: %lu\n", (uint64_t)expire);
 
 	return (expire ? expire + now : 0);
 }