unbreak the build (when warnings are enabled)

src/or/dirserv.c

@@ -1597,9 +1597,8 @@ dirserv_compute_performance_thresholds(digestmap_t *omit_as_sybil)
  * networkstatus_getinfo_by_purpose().
  */
 void
-dirserv_compute_bridge_flag_thresholds()
+dirserv_compute_bridge_flag_thresholds(void)
 {
-
   digestmap_t *omit_as_sybil = digestmap_new();
   dirserv_compute_performance_thresholds(omit_as_sybil);
   digestmap_free(omit_as_sybil, NULL);