/usr/lib/ghc-doc/hoogle/libghc-graphviz-doc.txt is in libghc-graphviz-doc 2999.18.0.2-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-graphviz-doc/html/graphviz.txt