AP_NavEKF3: always apply ekfGpsRefHgt corrections

ArduPilot#24039

 When 3rd bit is set, Ardupilot doesn't use ekfGpsRefHgt to convert GPS alt to local alt. But it still updates ekfGpsRefHgt in correctEkfOriginHeight. And the innovation used in the latter is constantly non-zero.

Author: peterbarker

libraries/AP_NavEKF3/AP_NavEKF3_Measurements.cpp

@@ -684,11 +684,7 @@ void NavEKF3_core::readGpsData()
     if (validOrigin) {
         gpsDataNew.lat = gpsloc.lat;
         gpsDataNew.lng = gpsloc.lng;
-        if ((frontend->_originHgtMode & (1<<2)) == 0) {
-            gpsDataNew.hgt = (ftype)((double)0.01 * (double)gpsloc.alt - ekfGpsRefHgt);
-        } else {
-            gpsDataNew.hgt = 0.01 * (gpsloc.alt - EKF_origin.alt);
-        }
+        gpsDataNew.hgt = (ftype)((double)0.01 * (double)gpsloc.alt - ekfGpsRefHgt);
         storedGPS.push(gpsDataNew);
         // declare GPS in use
         gpsIsInUse = true;