gyro_fft: silence initial sensor selection attempt

- early in startup the selected gyro may not be published yet

src/modules/gyro_fft/GyroFFT.cpp

@@ -140,7 +140,6 @@ bool GyroFFT::init()
 		}
 
 		if (!SensorSelectionUpdate(true)) {
-			PX4_WARN("sensor_gyro callback registration failed!");
 			ScheduleDelayed(500_ms);
 		}