doc: remove unnecessary module format comments

Now that the docs have toggles for CJS vs. ESM, there is no need to
include a comment explaining which module type is being used.

PR-URL: https://github.com/nodejs/node/pull/39219


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>