Update gaia6 from v6.0.0-rc3 to v6.0.0

[soareschen]

@JonathanLorimer I also had to switch the version of gomod2nix from your custom branch allow-custom-vendors to the main branch, otherwise the syncGoModules script would fail. Can you also check what is the issue with your version of gomod2nix?

[JonathanLorimer]

@soareschen I just added a commit switching back to my version, and I was able to syncGoModules and build gaia6. Can you post the error you are getting from my fork of gomod2nix? Also, I am in discussions with the maintainer of gomod2nix about getting my changes merged upstream, the discussion is taking place on discord, but we are trying to figure out if the custom vendors hack is really necessary.