[docs]: 404 when selecting older doc version < 23.1 from reference/index.html

# Documentation request
Given diataxis restructuring of docs, one cannot click docs versions prior to 23.1 from the following new index pages:
* reference/index.html
* development/index.html
* explanation/index.html
* howto/index.html
* tutorial/index.html

We probably need some readthedocs redirects setup to redirect to the appropriate top-level docs for each version in the above cases because that structure didn't previously exist

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*Reported from: https://cloudinit.readthedocs.io/en/latest/reference/index.html*