Look for an alternative to go-yaml/yaml

[toby]

It seems https://github.com/go-yaml/yaml was recently archived, we should probably find a fresh alternative.

[mntlty]

@toby running

$ go mod why -m gopkg.in/yaml.v3
# gopkg.in/yaml.v3
github.com/github/github-mcp-server/cmd/github-mcp-server
github.com/spf13/viper
github.com/spf13/viper/internal/encoding/yaml
gopkg.in/yaml.v3

the package is a result of our dependency on https://github.com/spf13/viper, they would have to update their codebase.

I see an open issue spf13/viper#1773 to do just that