Remove redundant initialization

CL: none

PUBLISHED_FROM=9d68cdc298c520798468b43a19c84251bd0c21b4

examples/mqtt_broker/mqtt_broker.c

@@ -31,7 +31,6 @@ int main(void) {
   struct mg_mqtt_broker brk;
 
   mg_mgr_init(&mgr, NULL);
-  mg_mqtt_broker_init(&brk, NULL);
 
   if ((c = mg_bind(&mgr, s_listening_address, ev_handler)) == NULL) {
     fprintf(stderr, "mg_bind(%s) failed\n", s_listening_address);