Revert "simulator: remove hack for diff_pressure noise"

This reverts commit 4a71984f77.

src/modules/simulator/simulator_mavlink.cpp

@@ -262,7 +262,9 @@ void Simulator::update_sensors(const mavlink_hil_sensor_t *imu)
 
 	RawAirspeedData airspeed = {};
 	airspeed.temperature = imu->temperature;
-	airspeed.diff_pressure = imu->diff_pressure;
+	// FIXME: diff_pressure needs some noise to pass preflight checks, so we just take the
+	//        noise from the gyro.
+	airspeed.diff_pressure = imu->diff_pressure + ((imu->ygyro > 0) ? 0.001f : 0.0f);
 
 	write_airspeed_data(&airspeed);
 }