test: refactor test-net-connect-buffer

- Use arrow functions, `common.mustCall()`
- Remove redundant `console.log()`s/turn them into assertions
- Use `common.expectsError()`

PR-URL: https://github.com/nodejs/node/pull/17710


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>