Copter: remove unused baro_climbrate variable

ArduCopter/Copter.h

@@ -466,7 +466,6 @@ private:
     float target_rangefinder_alt;   // desired altitude in cm above the ground
     bool target_rangefinder_alt_used; // true if mode is using target_rangefinder_alt
     int32_t baro_alt;            // barometer altitude in cm above home
-    float baro_climbrate;        // barometer climbrate in cm/s
     LowPassFilterVector3f land_accel_ef_filter; // accelerations for land and crash detector tests
 
     // filtered pilot's throttle input used to cancel landing if throttle held high

ArduCopter/sensors.cpp

@@ -6,7 +6,6 @@ void Copter::read_barometer(void)
     barometer.update();
 
     baro_alt = barometer.get_altitude() * 100.0f;
-    baro_climbrate = barometer.get_climb_rate() * 100.0f;
 
     motors->set_air_density_ratio(barometer.get_air_density_ratio());
 }