fix(pointcloud.vert): use snake_case for max_clip_boxes (#42)

- this reference to `max_clip_boxes` was capitalized, resulting in shader errors while attempting to use some of the clipping functionality.

Author: spelman7

src/materials/shaders/pointcloud.vert

@@ -496,7 +496,7 @@ void main() {
 
 	#if defined use_clip_box
 		bool insideAny = false;
-		for (int i = 0; i < MAX_CLIP_BOXES; i++) {
+		for (int i = 0; i < max_clip_boxes; i++) {
 			if (i == int(clipBoxCount)) {
 				break;
 			}