Remove public domain from the copyright file

[imciner2]

In 2016 the zuluCrypt-gui/md5 folder was removed, removing all public domain code. However the license file still lists it as a license used in the project https://github.com/mhogomchungu/zuluCrypt/blob/d1509759b8dc6e74d3700a5899fccf5c679df4a7/copyright#L33. It would be good to cleanup the license file by removing that.

[imciner2]

It is also present in the included Debian copyright file: https://github.com/mhogomchungu/zuluCrypt/blob/d1509759b8dc6e74d3700a5899fccf5c679df4a7/debian.upstream/copyright#L13

[mhogomchungu]

Done

https://github.com/mhogomchungu/zuluCrypt/commit/0570f59bbf1097ede28cf4e117f95e9d103d440c

[imciner2]

Thanks!