Refactor PRINTER_EVENT_LEDS, apply to M303 (#12038)

Co-Authored-By: Giuliano Zaro <gmagician@users.noreply.github.com>

Marlin/src/gcode/gcode.h

@@ -336,10 +336,6 @@ public:
     #define KEEPALIVE_STATE(n) NOOP
   #endif
 
-  #if ENABLED(PRINTER_EVENT_LEDS) && ENABLED(SDSUPPORT) && HAS_RESUME_CONTINUE
-    static bool lights_off_after_print;
-  #endif
-
   static void dwell(millis_t time);
 
 private: