Fix package registry processes link

Why is this change being made?

When the package group splitted in two teams a sub section called package registry was created.

At that time, a file was already existing ("package registry processes") at that location and it was moved elsewhere, see !113029 (merged).

The problem is that this existing page was linked in the package group page, see https://about.gitlab.com/handbook/engineering/development/ops/package/#-other-useful-links, there is a link called Package Registry processes. Because the location was replaced with the package registry team page, that link is pointing to the wrong location.

This MR fixes this by pointing the link to the new location.

Author Checklist

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