doc: stream.end(cb) cb can be invoked with error

Update docs that the optional callback passed to
`writable.end` can be invoked in case of an error as well.

PR-URL: https://github.com/nodejs/node/pull/32238
Fixes: https://github.com/nodejs/node/issues/31220


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>