Update glTF validator to 2.0.0-dev.3.3

dist/preview release/what's new.md

@@ -15,6 +15,7 @@
 - Added support for EXT_meshopt_compression for glTF loader. ([zeux](https://github.com/zeux))
 - Increased KHR_materials_transmission render target texture default size. ([Drigax](https://github.com/drigax))
 - Changed glTF loader to remove empty animation groups if there are no animation channels loaded with the given options. ([bghgary](https://github.com/bghgary))
+- Update glTF validator to `2.0.0-dev.3.3`. ([bghgary](https://github.com/bghgary))
 
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