AP_Vehicle: Remove unused flight stages

libraries/AP_Vehicle/AP_Vehicle.h

@@ -64,9 +64,7 @@ public:
             FLIGHT_TAKEOFF       = 1,
             FLIGHT_VTOL          = 2,
             FLIGHT_NORMAL        = 3,
-            FLIGHT_LAND_APPROACH = 4,
-            FLIGHT_LAND_PREFLARE = 5,
-            FLIGHT_LAND_FINAL    = 6,
+            FLIGHT_LAND          = 4,
             FLIGHT_ABORT_LAND    = 7
         };
     };