benchmark: coerce PORT to number

Without this fix net/tcp-raw-c2s.js aborts in environments where PORT
is defined. TCPWrap::Connect expects the third arg to be a UInt32.

PR-URL: https://github.com/nodejs/node/pull/23721


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>