test: remove call to `net.Socket.resume()`

In test parallel/child-process-fork-net2 `net.Socket.resume()` is not necessary
since `net.Socket.pause()` is never called.

PR-URL: https://github.com/nodejs/node/pull/8679
Refs: https://github.com/nodejs/node/issues/4640


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>