go/lint: remove gocyclo linter

[adamdecaf]

There is a flag to configure this, but it's deprecated:
https://github.com/golangci/golangci-lint/blob/7bbbe77e5e68cdbecad5e25fc44810afd8f3d48c/pkg/commands/run.go#L154-L155

# set some golangci-linter passthrough options
if [[ $GOLANGCI_FLAGS == "" ]];
then
    GOLANGCI_FLAGS="--gocyclo.min-complexity=50"
fi

Flag --gocyclo.min-complexity has been deprecated, flag will be removed soon, please, use .golangci.yml config

So we should just remove this. Setting .golangci.yml isn't something I want moov-io/infra's script to deal with.