Sponza licensing problem

[The Sponza asset](https://github.com/KhronosGroup/glTF-Sample-Assets/tree/main/Models/Sponza) is violating the terms of Crytek's license, and should be either removed, or it should be entirely replaced with the original source from Intel.

This was derived [from Crytek's repository](https://www.cryengine.com/marketplace/product/crytek/sponza-sample-scene), which has this license: All "Crytek assets are covered under the [CRYENGINE Limited License Agreement](https://www.cryengine.com/ce-terms)" which in turn forbids use of the asset for any purpose other than games developed within CryEngine.

Fortunately, the original asset was [created by Intel](https://www.intel.com/content/www/us/en/developer/topic-technology/graphics-research/samples.html), who made that version "available under the Creative Commons Attribution license." which is CCBY 4.0.

The current version of this asset should probably be removed, but it could be replaced with Intel's asset, which should be optimized since it currently weighs in a 3.6GB.

Start with the Sponza asset linked in the issue and review the cited Crytek and Intel source licenses. Determine whether the asset should be removed or replaced with Intel's Creative Commons Attribution version, and account for optimizing the replacement from its stated 3.6GB size; done means the repository no longer contains the licensing problem.

Written by the indexing model from the issue text.