doc: remove outdated notes on stdio in workers

Workers support `stdio` streams since the initial PR landed. These
lines are editing leftovers from before that and should be removed.

PR-URL: #23054
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: addaleax

doc/api/process.md

@@ -1797,8 +1797,6 @@ a [Writable][] stream.
 `process.stderr` differs from other Node.js streams in important ways, see
 [note on process I/O][] for more information.
 
-This feature is not available in [`Worker`][] threads.
-
 ## process.stdin
 
 * {Stream}
@@ -1831,8 +1829,6 @@ In "old" streams mode the `stdin` stream is paused by default, so one
 must call `process.stdin.resume()` to read from it. Note also that calling
 `process.stdin.resume()` itself would switch stream to "old" mode.
 
-This feature is not available in [`Worker`][] threads.
-
 ## process.stdout
 
 * {Stream}
@@ -1851,8 +1847,6 @@ process.stdin.pipe(process.stdout);
 `process.stdout` differs from other Node.js streams in important ways, see
 [note on process I/O][] for more information.
 
-This feature is not available in [`Worker`][] threads.
-
 ### A note on process I/O
 
 `process.stdout` and `process.stderr` differ from other Node.js streams in