Fix remaining deprecated GTK4 API calls for --with-werror compatibility

Co-authored-by: speed47 <218502+speed47@users.noreply.github.com>

src/rs01-window.c

@@ -80,7 +80,7 @@ static gboolean show_button_idle_func(gpointer data)
 {  Method *method = (Method*)data;
    RS01Widgets *wl = (RS01Widgets*)method->widgetList;
 
-   gtk_widget_show(wl->curveButton);
+   gtk_widget_set_visible(wl->curveButton, TRUE);
 
    return FALSE;
 }