README: example links to removed file

[Moredread]

In the README.md on line 221 (sorry I'm on mobile and can't seem to find a way to add a link) an example .sops.yaml is linked in your dot files repo, but it doesn't exist anymore. Also it references the old main branch name.

# Also see https://github.com/Mic92/dotfiles/blob/master/nixos/.sops.yaml

[Mic92]

Ah. And also I got rid of my .sops.yaml... Because I am now using a new cli frontend for sops-nix from here: https://clan.lol/blog/hello-world/