repl: add missing variable declaration

* Adds `let` to a variable declaration in a for loop
  that wasn't using anything.

* Declare the for initial expression in the for loop.

* Remove hoisted variables for loops.

PR-URL: https://github.com/nodejs/node/pull/29535


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>