Fix inconsistent #include style

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
diff --git a/compositor/shell.c b/compositor/shell.c
index 7bae944..f8305db 100644
--- a/compositor/shell.c
+++ b/compositor/shell.c
@@ -32,7 +32,7 @@
 #include <fcntl.h>
 #include <assert.h>
 
-#include "wayland-server.h"
+#include <wayland-server.h>
 #include "compositor.h"
 #include "desktop-shell-server-protocol.h"