/usr/share/doc/ocaml-findlib/ref-html is in libfindlib-ocaml-dev 1.5.5-2build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/ocaml-findlib/../libfindlib-ocaml-dev/ref-html
/usr/share/doc/ocaml-findlib/../libfindlib-ocaml-dev/ref-html