Don't include xserver-server-protocol.h

It was removed in 757d8aff27,
along with xserver protocol.

Signed-off-by: Mariusz Ceier <mceier+wayland@gmail.com>

xwayland/dnd.c

@@ -37,7 +37,6 @@
 
 #include "cairo-util.h"
 #include "compositor.h"
-#include "xserver-server-protocol.h"
 #include "hash.h"
 
 static void

xwayland/launcher.c

@@ -33,7 +33,6 @@
 #include <signal.h>
 
 #include "xwayland.h"
-#include "xserver-server-protocol.h"
 
 
 static int

xwayland/window-manager.c

@@ -38,7 +38,6 @@
 
 #include "cairo-util.h"
 #include "compositor.h"
-#include "xserver-server-protocol.h"
 #include "hash.h"
 
 struct wm_size_hints {