x11/xfce4-terminal: Fix build with WAYLAND option OFF

Import patch (already included in upstream repository [1]) to
properly fence gtk-layer-shell dependent code.

[1] https://gitlab.xfce.org/apps/xfce4-terminal/-/commit/b07d9546a08a3cd70b7e9aaad7a86256fbe32b8b

PR: 293731