Sub: remove unused calculation of longitude scale

ArduSub/commands.cpp

@@ -71,7 +71,7 @@ bool Sub::set_home(const Location& loc, bool lock)
     // init inav and compass declination
     if (!home_was_set) {
         // update navigation scalers.  used to offset the shrinking longitude as we go towards the poles
-        scaleLongDown = longitude_scale(loc);
+        scaleLongDown = loc.longitude_scale();
         // record home is set
         Log_Write_Event(DATA_SET_HOME);