WASM extension support is enabled by default

In 2.1, WASM support is enabled by default, there's no need to have a section explaining how to enable it before using it.

Although strictly speaking the ability to disable WASM is still there, we decided to hide it from the users, meaning that WASM Extension support not only is enabled by default, but is mandatory.

We are keeping the [internal, hidden] ability to disable it for now as an "escape hatch" if something serious happens, but with the intention of completely remove it in a future release.