simple-touch: do not include GL headers

since it doesn't use any of them. Fixes a build failure on systems,
where (E)GL headers are in non-standard path.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

clients/simple-touch.c

@@ -29,9 +29,7 @@
 #include <unistd.h>
 #include <sys/mman.h>
 
-#include <GLES2/gl2.h>
 #include <wayland-client.h>
-#include <wayland-egl.h>
 #include "../shared/os-compatibility.h"
 
 struct touch {