Fix changes introduced with wlroots version 0.10.0

[Hardy7cc]

As I updated my wlroots to version 0.10.0 I got a compilation error due to changes in wlroots. Have a look at :

• https://github.com/swaywm/wlroots/pull/1842
• https://github.com/swaywm/wlroots/commit/1724261910728bfa63eecb0f1729995c00c7ffe8#diff-88c44e7f4eb274cbeb46c2b811f5ea6e

In short:The variable layer in struct wlr_layer_surface_v1 is moved to wlr_layer_surface_v1_state

Only pull this if you change wlroots version too

[buffet]

Thanks!

I will keep this open until I have the time to actually allow layer-shell surfaces to change their layer.