tdf#146992 gtk_window_set_attached_to causing widgets to shift

which isn't desirable, just drop its use.

Change-Id: Ic29efa9e785cad3c221e0ef37816b8485979e719
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128957
Tested-by: Jenkins
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
diff --git a/vcl/unx/gtk3/gtkinst.cxx b/vcl/unx/gtk3/gtkinst.cxx
index 515eabb..bb6779a 100644
--- a/vcl/unx/gtk3/gtkinst.cxx
+++ b/vcl/unx/gtk3/gtkinst.cxx
@@ -9659,8 +9659,6 @@ GtkPositionType show_menu_older_gtk(GtkWidget* pMenuButton, GtkWindow* pMenu, co
    else
        x += nButtonWidth;

    gtk_window_set_attached_to(pMenu, pMenuButton);

    gtk_window_group_add_window(gtk_window_get_group(GTK_WINDOW(pToplevel)), pMenu);
    gtk_window_set_transient_for(pMenu, GTK_WINDOW(pToplevel));

@@ -9790,8 +9788,6 @@ bool show_menu_newer_gtk(GtkWidget* pComboBox, GtkWindow* pMenu, const GdkRectan
    gtk_coord x, y;
    gtk_widget_translate_coordinates(pComboBox, pToplevel, rAnchor.x, rAnchor.y, &x, &y);

    gtk_window_set_attached_to(pMenu, pComboBox);

    gtk_widget_realize(GTK_WIDGET(pMenu));
    gtk_window_group_add_window(gtk_window_get_group(GTK_WINDOW(pToplevel)), pMenu);
    gtk_window_set_transient_for(pMenu, GTK_WINDOW(pToplevel));