In Chapter "Physically Based Rendering and Lighting" the example from threejs is not found and returns 404 page.

[AnnaBurd]

Hello!

The first iframe on the page Physically Based Rendering and Lighting returns "404 not found error".

Describe the bug
See the red square on the screenshots:

To Reproduce

1. Go to the page the page Physically Based Rendering and Lighting and see the error.

Tested on desktop, mobile.

Suggestions
As the example was removed from three.js site, I suggest to delete the following lines from the book's markdown:

Thanks! If it's ok, I can open PR to fix the issue.