chore(docs): remove unused ExampleSnippetLazy component (#475)

ExampleSnippetLazy was never imported, registered as an MDX shortcode
(MdxLayout wires up the regular ExampleSnippet), or exported from the docs
component index — it was dead code. Removing it also clears the
react-hooks/set-state-in-effect and static-components lint errors it carried.

The stackblitz/codesandbox helpers it imported remain in use by
ExampleSnippet.

Author: mrholek