/usr/share/gtk-doc/html/gsf is in libgsf-1-dev 1.14.27-2ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gtk-doc/html/../../doc/libgsf-1-dev/html/gsf
/usr/share/gtk-doc/html/../../doc/libgsf-1-dev/html/gsf