doc: update http.md mention of socket

This commit is addressing the problem in issue #29948.

Fixes: https://github.com/nodejs/node/issues/29948
PR-URL: https://github.com/nodejs/node/pull/30155


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>