doc: fix links in vm.md

* Replace absolute link with relative link.
* Fix sorting in bottom references.

PR-URL: https://github.com/nodejs/node/pull/19721


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>