doc: add missing metadata for fs.open

PR-URL: https://github.com/nodejs/node/pull/19585
Refs: https://github.com/nodejs/node/pull/18801


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>