Missing layout in the bindless_texture example. (#2413)

This means the example should also work on intel
Xe and a generation before that (gma).

Author: einarf

arcade/examples/gl/bindless_texture.py

@@ -120,7 +120,7 @@ def __init__(self):
             // The texture handles in the buffer are 64 bit integers and are
             // automatically converted into sampler objects for us.
             struct TextureRef {
-                sampler2D tex; // 64 bit integer
+                layout (bindless_sampler) sampler2D tex; // 64 bit integer
             };
 
             // Shader storage buffer with texture handles