add missing `void` from jack_get_time prototype

jack.h

@@ -1271,7 +1271,7 @@ jack_nframes_t jack_time_to_frames(const jack_client_t *client, jack_time_t) JAC
  * 
  * The value returned is guaranteed to be monotonic, but not linear.
  */
-jack_time_t jack_get_time() JACK_OPTIONAL_WEAK_EXPORT;
+jack_time_t jack_get_time(void) JACK_OPTIONAL_WEAK_EXPORT;
 
 /*@}*/