/usr/share/gtk-doc/ is in libpanel-applet-doc 1:3.26.0-1ubuntu5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gtk-doc/html/
/usr/share/gtk-doc/html/libpanel-applet/
/usr/share/gtk-doc/html/libpanel-applet/add_to_panel.png
/usr/share/gtk-doc/html/libpanel-applet/annotation-glossary.html
/usr/share/gtk-doc/html/libpanel-applet/api-index-3-18.html
/usr/share/gtk-doc/html/libpanel-applet/api-index-3-22.html
/usr/share/gtk-doc/html/libpanel-applet/api-index-3-4.html
/usr/share/gtk-doc/html/libpanel-applet/api-index-full.html
/usr/share/gtk-doc/html/libpanel-applet/ch10.html
/usr/share/gtk-doc/html/libpanel-applet/deprecated-api-index.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.concepts.applet-instances.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.concepts.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.context-menu.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.context-menu.setup.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.example.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.in-out-process.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.install.build-system.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.install.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.integration.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.intro.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.introspection.html
/usr/share/gtk-doc/html/libpanel-applet/getting-started.settings.html
/usr/share/gtk-doc/html/libpanel-applet/home.png
/usr/share/gtk-doc/html/libpanel-applet/index.html
/usr/share/gtk-doc/html/libpanel-applet/left-insensitive.png
/usr/share/gtk-doc/html/libpanel-applet/left.png
/usr/share/gtk-doc/html/libpanel-applet/libpanel-applet-Panel-Applet-Factory.html
/usr/share/gtk-doc/html/libpanel-applet/libpanel-applet-Panel-Applet.html
/usr/share/gtk-doc/html/libpanel-applet/libpanel-applet.devhelp2
/usr/share/gtk-doc/html/libpanel-applet/object-tree.html
/usr/share/gtk-doc/html/libpanel-applet/overview.html
/usr/share/gtk-doc/html/libpanel-applet/port-gnome2.dbus.html
/usr/share/gtk-doc/html/libpanel-applet/port-gnome2.dbus.migrate-menus-to-gaction.html
/usr/share/gtk-doc/html/libpanel-applet/port-gnome2.dbus.remove-libbonobo-factory.html
/usr/share/gtk-doc/html/libpanel-applet/port-gnome2.html
/usr/share/gtk-doc/html/libpanel-applet/reference.html
/usr/share/gtk-doc/html/libpanel-applet/right-insensitive.png
/usr/share/gtk-doc/html/libpanel-applet/right.png
/usr/share/gtk-doc/html/libpanel-applet/style.css
/usr/share/gtk-doc/html/libpanel-applet/up-insensitive.png
/usr/share/gtk-doc/html/libpanel-applet/up.png