SITL: fixed GPS heading in simulated UBlox

longitude scale does not apply to velocity->heading conversions

libraries/Desktop/support/sitl_gps.cpp

@@ -144,8 +144,7 @@ void sitl_update_gps(double latitude, double longitude, float altitude,
 #define sqr(x) ((x)*(x))
 	velned.speed_2d = sqrt(sqr(speedN)+sqr(speedE)) * 100;
 	velned.speed_3d = velned.speed_2d;
-        lon_scale = cos(ToRad(latitude));
-	velned.heading_2d = ToDeg(atan2(lon_scale*speedE, speedN)) * 100000.0;
+	velned.heading_2d = ToDeg(atan2(speedE, speedN)) * 100000.0;
 	if (velned.heading_2d < 0.0) {
 		velned.heading_2d += 360.0 * 100000.0;
 	}