M31 serial output is now always in EN

Marlin/Marlin_main.cpp

   lcd_setstatus(buffer);
 
   SERIAL_ECHO_START;
-  SERIAL_ECHOPGM(MSG_PRINT_TIME " ");
+  SERIAL_ECHOPGM("Print time: ");
   SERIAL_ECHOLN(buffer);
 
   thermalManager.autotempShutdown();