docs: rename manual to unmanaged, drop equinix

[tmihoc]

When Juju 4 is released (some time in the next two weeks), the juju.is/docs page (now https://canonical.com/juju/docs) needs to be updated as follows:

• Equinix needs to be dropped (it's no longer supported (or available, for that matter))
• Manual needs to be renamed to "Unmanaged (the changes in the code haven't been made yet, and might end up not being made, but for now the plan is that they will be made, so this PR anticipates that)

This PR makes both these changes.

Note: The line alignment might have to be adjusted in light of Equinix going away.

[webteam-app]

Demo

Jenkins

demos.haus

[tmihoc]

This repo is about to be archived. The changes need to target https://github.com/canonical/canonical.com/tree/main/templates/juju . This PR does that: canonical/canonical.com#2047