Docs: update link to SetupHooks RFC

The proposal has been accepted, but its final location is in the 'rfc'
subdirectory instead of the 'proposals' subdirectory. This simply
updates the link in the Cabal documentation.

Author: sheaf

doc/cabal-package-description-file.rst

@@ -2813,7 +2813,7 @@ while a basic ``SetupHooks.hs`` file might look like the following:
 
 Refer to the `Hackage documentation for the Distribution.Simple.SetupHooks module <https://hackage.haskell.org/package/Cabal-hooks/docs/Distribution-Simple-SetupHooks.html>`__
 for an overview of the ``Hooks`` API. Further motivation and a technical overview
-of the design is available in `Haskell Tech Proposal #60 <https://github.com/haskellfoundation/tech-proposals/blob/main/proposals/accepted/060-replacing-cabal-custom-build.md>`__ .
+of the design is available in `Haskell Tech Proposal #60 <https://github.com/haskellfoundation/tech-proposals/blob/main/rfc/060-replacing-cabal-custom-build.md>`__ .
 
 .. _custom-setup: