wayland/activation: Fix signal callback signature
Parameter notify signals have a GParamSpec as second parameter.
Closes: #3523 (closed) Fixes: c166b3fc ("wayland/activation: Apply xdg-activation request when window gets mapped")
Parameter notify signals have a GParamSpec as second parameter.
Closes: #3523 (closed) Fixes: c166b3fc ("wayland/activation: Apply xdg-activation request when window gets mapped")