Cleanup the go.mod for etcdctl
Cleanup the go.mod for etcdctl

etcdctl doesn't depend on the following packages at all,
1. go.etcd.io/etcd/client/v2
2. go.etcd.io/etcd/etcdutl/v3
3. go.etcd.io/etcd/raft/v3
4. go.etcd.io/etcd/server/v3

Signed-off-by: Benjamin Wang <a1713d12b1b05630690f22cadfd282d625d8acb2@vmware.com>

etcd-io/etcd,ajityagaty/etcd,etcd-io/etcd,ajityagaty/etcd,ajityagaty/etcd,etcd-io/etcd