Merge pull request #1641 from plone/linkcheck-2024-03-15

`https://classic.demo.plone.org` flip-flopped

Author: stevepiercy

docs/install/index.md

@@ -21,7 +21,7 @@ In this part of the documentation, you can find how to {ref}`try Plone <install-
 Choose a version to demo.
 
 -   [Plone 6 with Volto frontend](https://demo.plone.org/)
--   [Plone 6 with Classic UI](https://classic.demo.plone.org)
+-   [Plone 6 with Classic UI](https://classic.demo.plone.org/en)
 
 
 (install-index-getting-started-label)=