/usr/lib/ghc-doc/hoogle/http-reverse-proxy.txt is in libghc-http-reverse-proxy-doc 0.2.0-1build6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-http-reverse-proxy-doc/html/http-reverse-proxy.txt