/lib/udev/rules.d/60-i2c-tools.rules is in i2c-tools 3.1.2-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1
SUBSYSTEM=="i2c-dev",KERNEL=="i2c-[0-9]*", GROUP="i2c", MODE="0660"