Remove the extra save confirmation

This code was transferred from the Pokecommunity thread.

Open start_menu.c and look for the function SaveFileExistsCallback

else
    {
-       ShowSaveMessage(gText_AlreadySavedFile, SaveConfirmOverwriteCallback);
+       sSaveDialogCallback = SaveSavingMessageCallback;
    }

    return SAVE_IN_PROGRESS;
}