/usr/share/doc/ is in initramfs-tools 0.99ubuntu13.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/initramfs-tools/
/usr/share/doc/initramfs-tools/HACKING
/usr/share/doc/initramfs-tools/maintainer-notes.html
/usr/share/doc/initramfs-tools/TODO
/usr/share/doc/initramfs-tools/copyright
/usr/share/doc/initramfs-tools/examples/
/usr/share/doc/initramfs-tools/examples/modules
/usr/share/doc/initramfs-tools/examples/example_script
/usr/share/doc/initramfs-tools/examples/example_hook
/usr/share/doc/initramfs-tools/examples/framebuffer
/usr/share/doc-base/initramfs-maintainer
/usr/share/doc/initramfs-tools/changelog.gz
/usr/share/doc/initramfs-tools/NEWS.Debian.gz