fs: make URL paths no longer experimental

PR-URL: #18591
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: jasnell

doc/api/fs.md

@@ -164,9 +164,6 @@ example `fs.readdirSync('c:\\')` can potentially return a different result than
 <!-- YAML
 added: v7.6.0
 -->
-
-> Stability: 1 - Experimental
-
 For most `fs` module functions, the `path` or `filename` argument may be passed
 as a WHATWG [`URL`][] object. Only [`URL`][] objects using the `file:` protocol
 are supported.