Copyright for partman-auto-raid source package in Focal

This package is under the GNU GPL version 2, or any later
version at your option.
On Debian system, the GPL is available in 
/usr/share/common-licenses/GPL-2

partman-auto-raid was mostly based on existing code from partman-auto,
partman-auto-md and mdcfg. The package was created and combining code
was written by Simon Huggins .