doc: do not mention TCP in the allowHalfOpen option description

The `allowHalfOpen` option works in the same way for both TCP and IPC
connections.

PR-URL: https://github.com/nodejs/node/pull/38360
Fixes: https://github.com/nodejs/node/issues/38307


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>