debugger: remove unused code

Remove code that was for when `node-inspect` was called as a standalone
process.

PR-URL: https://github.com/nodejs/node/pull/38161
Refs: https://github.com/nodejs/node/discussions/36481


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Michaël Zasso <targos@protonmail.com>