doc: update core-validate-commit link in guide

PR-URL: https://github.com/nodejs/node/pull/35938


Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Mary Marchini <oss@mmarchini.me>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>