Issue:
This documents ECMAScript 2017 (ECMA-262) Link going to 404 pages.
Why:
I don’t know why this happen,
But maybe reference link are deleted
{{SpecName('ES8', '#sec-async-function-definitions', 'async function')}}
will go https://tc39.github.io/ecma262/2017/#sec-async-function-definitions.
So if can change, ES8 specifications URL are
https://tc39.github.io/ecma262/2018/#sec-async-function-definitions
Thanks.