MC LandDetector: remove dependency on MPC_LAND_SPEED and MPC_LAND_CRWL

Don't consider these params for vertical speed threshold,
and instead increase the default for LNDMC_Z_VEL_MAX and
use solely that one. Makes the land detector outcome more
predictable and its interal logic simpler, while the new
default tuning is resulting in about the same vz threshold
as before.

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/land_detector/MulticopterLandDetector.h

@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (c) 2013-2016 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2013-2022 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -95,8 +95,6 @@ private:
 		param_t minThrottle;
 		param_t hoverThrottle;
 		param_t minManThrottle;
-		param_t landSpeed;
-		param_t crawlSpeed;
 		param_t useHoverThrustEstimate;
 	} _paramHandle{};
 
@@ -104,8 +102,6 @@ private:
 		float minThrottle;
 		float hoverThrottle;
 		float minManThrottle;
-		float landSpeed;
-		float crawlSpeed;
 		bool useHoverThrustEstimate;
 	} _params{};