Remove [removal-of-types] docs page, and point to 7x docs (#53670)

Given that types have been removed entirely in 8.0, we don't need a detailed page
explaining what they are and why they are going away. This commit replaces the
page with a short paragraph saying that types are no longer supported, and a link
to the [removal-of-types] page in 7x

Relates to #41059

Author: romseygeek