/usr/share/gtk-doc/html/libags_gui is in libags-gui-doc 1.4.24-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gtk-doc/html/../../doc/libags-gui-doc/api
/usr/share/gtk-doc/html/../../doc/libags-gui-doc/api