Update Italian language (#19953)

Marlin/src/lcd/language/language_it.h

  *
  * LCD Menu Messages
  * See also https://marlinfw.org/docs/development/lcd_language.html
+ *
+ * Substitutions are applied for the following characters when used
+ * in menu items that call lcd_put_u8str_ind_P with an index:
+ *
+ *   = displays  '0'....'10' for indexes 0 - 10
+ *   ~ displays  '1'....'11' for indexes 0 - 10
+ *   * displays 'E1'...'E11' for indexes 0 - 10 (By default. Uses LCD_FIRST_TOOL)
  */
 
 #define DISPLAY_CHARSET_ISO10646_1
   PROGMEM Language_Str MSG_AUTO_HOME_Z                     = _UxGT("Home asse Z");
   PROGMEM Language_Str MSG_AUTO_Z_ALIGN                    = _UxGT("Allineam.automat. Z");
   PROGMEM Language_Str MSG_ASSISTED_TRAMMING               = _UxGT("Tramming assistito");
+  PROGMEM Language_Str MSG_ITERATION                       = _UxGT("Iterazione G34: %i");
+  PROGMEM Language_Str MSG_DECREASING_ACCURACY             = _UxGT("Precis.in calo!");
+  PROGMEM Language_Str MSG_ACCURACY_ACHIEVED               = _UxGT("Precis.raggiunta");
   PROGMEM Language_Str MSG_LEVEL_BED_HOMING                = _UxGT("Home assi XYZ");
   PROGMEM Language_Str MSG_LEVEL_BED_WAITING               = _UxGT("Premi per iniziare");
   PROGMEM Language_Str MSG_LEVEL_BED_NEXT_POINT            = _UxGT("Punto successivo");
   PROGMEM Language_Str MSG_REHEATING                       = _UxGT("Riscaldando...");
 
   PROGMEM Language_Str MSG_PROBE_WIZARD                    = _UxGT("Proc.guid.sonda Z");
+  PROGMEM Language_Str MSG_SOUND                           = _UxGT("Suono");
 }