doc: deprecate http finished

PR-URL: https://github.com/nodejs/node/pull/28679
Refs: https://github.com/nodejs/node/issues/28651


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>