fix clipboard store on VteTerminal closing
vte trying hard to have its clipboard contents prevail on finalization, at https://gitlab.gnome.org/GNOME/vte/-/blob/c346a0dd6a/src/vte.cc#L8070-8087. In the gnome-terminal case, this happens when the window is being destroyed, and the compositor no longer considers the surface focused.
These requests do get ignored on Wayland, leaving the client in an inconsistent state where it is permanently led to think it owns the selection. I have a fix for Mutter to cancel those wl_data_sources and get GTK out of that trap, but I think vte should not do that, and use gtk_clipboard_store() instead.