Remove heartbeat log from demo app

src/sdl.c

@@ -85,13 +85,6 @@ int main(int argc, char* argv[]) {
                             printf("\tVision type %d\n", fragment.message.push.vision.type);
                             printf("\tVision status %d\n", fragment.message.push.vision.status);
                             break;
-                        case SDK_HEARTBEAT_CMD:
-                            if(fragment.message.resp.heartbeat.retcode) {
-                                printf("ERROR: Heartbeat error\n");
-                                break;
-                            }
-                            printf("Heartbeat\n");
-                            break;
                         case STREAM_CTRL_CMD:
                             if(fragment.message.resp.stream.retcode) {
                                 printf("ERROR: Stream not enabled\n");