[wayland] Drop pointless xwayland connection check

Xwayland can operate in two modes - rootless and rootful. When Xwayland
operates in the rootful mode, a container window is created where all
native X11 clients are placed. The container window is an xdg-toplevel
surface. Most compositors are not interested in rootful mode.

When Xwayland operates in the rootless mode, every X11 window is going
to be represented with a Wayland surface that has no role assigned to it.
In order to associate a wayland surface with an X11 window, Xwayland
will send a client message of type WL_SURFACE_ID.

Since we want Xwayland operate only in rootless mode, the check that
verifies that a newly created xdg-toplevel surface belongs to Xwayland
is pointless. We are never going to hit that case.