FlightTaskAuto: remove unused member variable

src/lib/FlightTasks/tasks/FlightTaskAuto.hpp

@@ -90,8 +90,6 @@ private:
 	DEFINE_PARAMETERS_CUSTOM_PARENT(FlightTask,
 					(ParamFloat<px4::params::MPC_XY_CRUISE>) MPC_XY_CRUISE); /**< Default mc cruise speed.*/
 
-	map_projection_reference_s _reference; /**< Reference frame from global to local. */
-
 	map_projection_reference_s _reference_position{}; /**< Structure used to project lat/lon setpoint into local frame. */
 	float _reference_altitude = NAN;  /**< Altitude relative to ground. */
 	hrt_abstime _time_stamp_reference = 0; /**< time stamp when last reference update occured. */