Drop extraneous calls to lcd_update

Marlin/Marlin_main.cpp

     #if ENABLED(ULTIPANEL)
       powersupply = true;
       LCD_MESSAGEPGM(WELCOME_MSG);
-      lcd_update();
     #endif
   }
 
       powersupply = false;
     #endif
     LCD_MESSAGEPGM(MACHINE_NAME " " MSG_OFF ".");
-    lcd_update();
   #endif
 }