Outdated cabal documentation

The [original Cabal proposal](https://www.haskell.org/cabal/proposal/index.html) (which must be from about 20 years ago) appears on Haskell.org. It is not clearly marked as an archive of a historical document. [A user tried to follow it to enable `FlexibleContexts`](https://www.reddit.com/r/haskell/comments/hwy8ux/how_to_draw_line_charts_with_interactive_comments/fz337na/), specifically the [The Cabal simple build infrastructure](https://www.haskell.org/cabal/proposal/x611.html) section.

Is it possible to perhaps just delete it and let the internet archive preserve it for posterity? Alternatively, if as a historical document it should be preserved, could it be clearly marked as a historical document, not for up-to-date use, and perhaps even moved to another domain (haskell-history.org?).

It's really, really confusing for users to come across documentation that is not up-to-date. See [an example that occurred just today](https://mail.haskell.org/pipermail/haskell-cafe/2020-December/133139.html).