stream: removed outdated TODO

Was resolved in https://github.com/nodejs/node/commit/e559842188f541b884abff2ffad4d2d3e1b841a6.

PR-URL: https://github.com/nodejs/node/pull/31701


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>