doc: update debugger.md description and examples

The console captures in debugger.md are out of date, showing the
wrapper:

  function (exports, require, module, __filename, __dirname) {

That wrapper is no longer shown in debug sessions.

This also shortens and simplifies the description of the debugger in the
lede.

PR-URL: https://github.com/nodejs/node/pull/39661


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>