/usr/lib/ghc-doc/hoogle/libghc-cabal-helper-doc.txt is in libghc-cabal-helper-doc 0.6.2.0-4build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-cabal-helper-doc/html/cabal-helper.txt