remove incorrect statement about dns addresses in README

[marten-seemann]

We even have a test case that we cannot dial dns addresses:

go-tcp-transport/tcp_test.go

Lines 40 to 60 in 5c96425

	func TestTcpTransportCantDialDNS(t *testing.T) {
	for i := 0; i < 2; i++ {
	dnsa, err := ma.NewMultiaddr("/dns4/example.com/tcp/1234")
	if err != nil {
	t.Fatal(err)
	}
	_, sm := makeInsecureMuxer(t)
	tpt := NewTCPTransport(&tptu.Upgrader{
	Secure: sm,
	Muxer: new(mplex.Transport),
	})
	if tpt.CanDial(dnsa) {
	t.Fatal("shouldn't be able to dial dns")
	}
	envReuseportVal = false
	}
	envReuseportVal = true
	}

[Stebalien]

Hm. Yeah, we handle resolution at a higher layer.