doc: add the valid link for curl(1) in repl.md

The current autoinserted link leads to 404 page.

PR-URL: https://github.com/nodejs/node/pull/10244


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