/etc/clamav-unofficial-sigs.conf.d/README is in clamav-unofficial-sigs 3.7.2-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # Please see the README.Debian file for more info:
# /usr/share/doc/clamav-unofficial-sigs/README.Debian
|