/usr/lib/ghc-doc/hoogle/libghc-servant-server-doc.txt is in libghc-servant-server-doc 0.8.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-servant-server-doc/html/servant-server.txt