/usr/lib/ghc-doc/hoogle/libghc-ftphs-doc.txt is in libghc-ftphs-doc 1.0.9.1-8build3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-ftphs-doc/html/ftphs.txt