doc,stream: split finish and end events into separate entries

The stream doc has the only instance in our docs where two events are
combined into a single entry. Split them into separate adjacent entries.

PR-URL: https://github.com/nodejs/node/pull/33881


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>