cmd/geth: remove network id from version cmd

It was reflective only of the Default setting,
and not chain aware.

cmd/geth/misccmd.go

@@ -117,7 +117,6 @@ func version(ctx *cli.Context) error {
 	}
 	fmt.Println("Architecture:", runtime.GOARCH)
 	fmt.Println("Protocol Versions:", eth.ProtocolVersions)
-	fmt.Println("Network Id:", eth.DefaultConfig.NetworkId)
 	fmt.Println("Go Version:", runtime.Version())
 	fmt.Println("Operating System:", runtime.GOOS)
 	fmt.Printf("GOPATH=%s\n", os.Getenv("GOPATH"))