doc: remove parenthetical in onboarding-extras

Remove "(I prefer the former)" from onboarding-extras. Without any
explanation as to why one might prefer A over B, it probably raises more
questions than it answers.

PR-URL: https://github.com/nodejs/node/pull/20393


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>