http: remove redundant call to socket.setTimeout()

`Socket.prototype.setTimeout()` clears the previous timer before setting
a new one.

Refs: https://github.com/nodejs/node/pull/25748#discussion_r253393234

PR-URL: https://github.com/nodejs/node/pull/25928


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>