add varnish deprecated versions section

[gilzow]

Priority

3 - Not urgent - can be addressed as team bandwidth permits

Where should the changes be made?

https://docs.upsun.com/add-services/varnish.html#supported-versions
https://fixed.docs.upsun.com/add-services/varnish.html#supported-versions

What exactly should be updated?

we are missing a "deprecated versions" section to the varnish pages

Optional: Additional context

Deprecated versions are listed in registry.json and are still available as images, but we dont have a table for the deprecated versions.