/etc/fonts/conf.d/90-fonts-unfonts-extra.conf is in fonts-unfonts-extra 1.0.3.is.1.0.2-080608-4ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/fonts/conf.d/../conf.avail/90-fonts-unfonts-extra.conf