✏️ Fix LCD sleep conditional (#24685)

Marlin/src/inc/Conditionals_adv.h

 #if ALL(HAS_RESUME_CONTINUE, PRINTER_EVENT_LEDS, SDSUPPORT)
   #define HAS_LEDS_OFF_FLAG 1
 #endif
-#ifdef DISPLAY_SLEEP_MINUTES || TOUCH_IDLE_SLEEP_MINS
+#if DISPLAY_SLEEP_MINUTES || TOUCH_IDLE_SLEEP_MINS
   #define HAS_DISPLAY_SLEEP 1
 #endif
 #if HAS_DISPLAY_SLEEP || LCD_BACKLIGHT_TIMEOUT_MINS