doc: change lang info string in fs JS snippets

Refs: https://github.com/nodejs/remark-preset-lint-node/pull/176

PR-URL: https://github.com/nodejs/node/pull/37605
Refs: https://github.com/nodejs/node/pull/37162


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Danielle Adams <adamzdanielle@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>