Update Italian language (#14440)

Marlin/src/lcd/language/language_it.h

@@ -78,6 +78,10 @@
 #define MSG_LASER_OFF                       _UxGT("Laser Off")
 #define MSG_LASER_ON                        _UxGT("Laser On")
 #define MSG_LASER_POWER                     _UxGT("Potenza laser")
+#define MSG_SPINDLE_MENU                    _UxGT("Controllo mandrino")
+#define MSG_SPINDLE_OFF                     _UxGT("Mandrino Off")
+#define MSG_SPINDLE_ON                      _UxGT("Mandrino On")
+#define MSG_SPINDLE_POWER                   _UxGT("Potenza mandrino")
 #define MSG_SPINDLE_REVERSE                 _UxGT("Inverti mandrino")
 #define MSG_SWITCH_PS_ON                    _UxGT("Accendi aliment.")
 #define MSG_SWITCH_PS_OFF                   _UxGT("Spegni aliment.")