airspeed calibration: instruct to blow into front of pitot

... rather than across it

src/modules/commander/airspeed_calibration.cpp

@@ -199,7 +199,7 @@ int do_airspeed_calibration(orb_advert_t *mavlink_log_pub)
 	/* wait 500 ms to ensure parameter propagated through the system */
 	px4_usleep(500 * 1000);
 
-	calibration_log_critical(mavlink_log_pub, "[cal] Blow across front of pitot without touching");
+	calibration_log_critical(mavlink_log_pub, "[cal] Blow into front of pitot without touching");
 
 	calibration_counter = 0;