Go gRPC authentication - fix example

[polandll]

Per Michael Penick:
go-auth-secure.go

passwd := "cassandra"

config := &tls.Config{
 	InsecureSkipVerify: false,

false is the default so this doesn't need to be set. Here's one recommended way of specifying TLS in the go grpc client: https://github.com/grpc/grpc-go/blob/master/Documentation/grpc-auth-support.md#enabling-tls-on-a-grpc-client

So, I need to research and fix this example.