Use sha256 over md5

[domenkozar]

md5 is deprecated, let's use sha256 hash for source files :)

[proger]

Deprecated by what? nixpkgs?

[domenkozar]

See NixOS/nixpkgs#4491

[proger]

Thanks

[proger]

Currently we're using PyPI package metadata to get the md5 for the tarball and we need to compute the hash manually and/or using smth like nix-prefetch-url.

Putting this comment to let people stopping by know that's not a super quick win right now.

[c0bw3b]

@domenkozar I think we can close this now?
Only md5 left in the tree is inside libreoffice and it's only used to compose a name or a URL.