doc: fixup process.binding deprecation code

PR-URL: https://github.com/nodejs/node/pull/22062


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>