tools,doc: enable ecmaVersion 2021 in acorn parser

PR-URL: https://github.com/nodejs/node/pull/35994


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Derek Lewis <DerekNonGeneric@inf.is>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>