http2: remove `streamError` from docs

`streamError` was removed quite some time ago but the docs and
code comments weren't updated. Fix that.

Fixes: https://github.com/nodejs/node/issues/20211

PR-URL: https://github.com/nodejs/node/pull/22246


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>