/etc/fonts/conf.d/10-hinting.conf is in fontconfig-config 2.11.94-0ubuntu1.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/fonts/conf.d/../conf.avail/10-hinting.conf
/etc/fonts/conf.d/../conf.avail/10-hinting.conf