doc: clarify fs permissions only affect fs module

As far as I can tell, the permission model implementation currently
does not restrict all file system operations but only those through
the fs module. WASI, for example, bypasses the permission model
entirely.

PR-URL: #47782
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>

doc/api/permissions.md

@@ -465,8 +465,8 @@ The available permissions are documented by the [`--experimental-permission`][]
 flag.
 
 When starting Node.js with `--experimental-permission`,
-the ability to access the file system, spawn processes, and
-use `node:worker_threads` will be restricted.
+the ability to access the file system through the `fs` module, spawn processes,
+and use `node:worker_threads` will be restricted.
 
 ```console
 $ node --experimental-permission index.js