Tracker: use AP_RTC

Tracker: AP_GPS now sets the system time directly

AntennaTracker/sensors.cpp

@@ -83,14 +83,6 @@ void Tracker::update_GPS(void)
                 current_loc = gps.location();
                 set_home(current_loc);
 
-                // set system clock for log timestamps
-                uint64_t gps_timestamp = gps.time_epoch_usec();
-                
-                hal.util->set_system_clock(gps_timestamp);
-                
-                // update signing timestamp
-                GCS_MAVLINK::update_signing_timestamp(gps_timestamp);
-
                 if (g.compass_enabled) {
                     // Set compass declination automatically
                     compass.set_initial_location(gps.location().lat, gps.location().lng);