/usr/lib/ghc-doc/hoogle/mwc-random.txt is in libghc-mwc-random-doc 0.11.0.0-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-mwc-random-doc/html/mwc-random.txt