worker: remove redundant function call to `setupPortReferencing`

There is no need to call `setupPortReferencing` in `setupChild`
as which has been called with the same arguments in the `oninit`
prototype method of `MessagePort`.

PR-URL: https://github.com/nodejs/node/pull/22298


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