Fix debug message for 3-point leveling

Marlin/Marlin_main.cpp

       } //yProbe
 
       #if ENABLED(DEBUG_LEVELING_FEATURE)
-        if (DEBUGGING(LEVELING)) DEBUG_POS("> probing complete", current_position);
+        if (DEBUGGING(LEVELING)) SERIAL_ECHOLNPGM("> 3-point Leveling");
       #endif
 
       #if ENABLED(DELTA)