Clarify handbook page on acquisitions re: soft-landings

The current page on acquisitions (https://about.gitlab.com/handbook/acquisitions/) only describes the soft-landing acquisition process, without making it clear that there are other types of acquisitions, but the process will be different. Our blog post on the subject does mention other options at the bottom.

Perhaps we can move existing content to a specific "soft-landing" page and keep the top level page more generic. We're not able to describe other types of acquisition with a lot of detail as each would likely be unique, but there are probably some commonalities we can describe, such as fitting into our DevOps Platform definition.