/usr/lib/ghc-doc/hoogle/libghc-monadlib-doc.txt is in libghc-monadlib-doc 3.7.3-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-monadlib-doc/html/monadLib.txt