AP_NavEKF3: set-origin failure commend improved

Co-authored-by: Peter Barker <pb-gh@barker.dropbear.id.au>

libraries/AP_NavEKF3/AP_NavEKF3.cpp

@@ -1395,7 +1395,7 @@ bool NavEKF3::setOriginLLH(const Location &loc)
     if (common_origin_valid) {
         // we don't allow setting the EKF origin if it has already been set
         // this is to prevent causing upsets from a shifting origin.
-        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "EKF3 refusing set origin");
+        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "EKF3: origin already set");
         return false;
     }
     bool ret = false;