AP_NavEKF: remove unwanted co-variance reset

The co-variance resets required following a velocity and position state reset is now performed in the stte reset function

libraries/AP_NavEKF2/AP_NavEKF2_Control.cpp

@@ -143,10 +143,9 @@ void NavEKF2_core::setAidingMode()
             // reset the last valid position fix time to prevent unwanted activation of GPS glitch logic
             lastPosPassTime_ms = imuSampleTime_ms;
         }
-        // Reset all position, velocity and covariance
+        // Reset the position and velocity
         ResetVelocity();
         ResetPosition();
-        CovarianceInit();
 
     }