kwineffects: Stop linking kwayland-server

As is, libkwineffects doesn't use any specific apis in kwayland-server,
it simply "forwards" wayland display and surfaces from libkwin. Given
that, there is no need to link libkwineffects with kwayland-server. If
an effect needs to access wayland specific stuff, it can link explicitly
against kwayland-server.

The main motivation behind this change is to further loosen up
dependencies between various kwin components and kwayland-server so the
latter can be moved back to kwin.