Fix Cancel Objects index display (zero-based) (#18841)

Marlin/src/feature/cancel_object.cpp

 
   #if HAS_DISPLAY
     if (active_object >= 0)
-      ui.status_printf_P(0, PSTR(S_FMT " %i"), GET_TEXT(MSG_PRINTING_OBJECT), int(active_object + 1));
+      ui.status_printf_P(0, PSTR(S_FMT " %i"), GET_TEXT(MSG_PRINTING_OBJECT), int(active_object));
     else
       ui.reset_status();
   #endif