
This reverts commit 35d92e0fac
.
This turned out to cause trouble, because it can prevent
MetaWaylandSurface::applied_state.subsurface_branch_node from ever
getting linked up for a sub-surface.
It shouldn't be necessary anyway, since permanently_unmap_subsurface /
wl_subcompositor_get_subsurface reset the sub-surface state as defined
by the protocol.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3737>