commander: reword nav failure message

src/modules/commander/Commander.cpp

@@ -4041,7 +4041,7 @@ void Commander::estimator_check()
 						if (!_nav_test_failed && hrt_elapsed_time(&_time_last_innov_pass) > 1_s) {
 							// if the innovation test has failed continuously, declare the nav as failed
 							_nav_test_failed = true;
-							mavlink_log_emergency(&_mavlink_log_pub, "Navigation failure! Recalibrate sensors");
+							mavlink_log_emergency(&_mavlink_log_pub, "Navigation failure! Land and recalibrate sensors");
 						}
 					}
 				}