feat: Remove Page workaround UI from List component

[DafyddLlyr]

What does this PR do?

• Removes the isPageComponent variable from the List component, and the associated UI changes
• Adds validation to the List editor modal - a List schema must allow multiple items

Why?

This was always a bit of unintended workaround, and we're now explicitly removing this as a Page component is likely a more suitable option.

This PR won't break any existing flows or behaviours, it will simply stop pseudo-Page components from being generated. Once the feature flag is removed from the Page feature, we can migrate any flows using the AdvertConsent schema to be a Page, and remove this option from the List schema folder.

[github-actions[bot]]

Removed vultr server and associated DNS entries