minor issue: fix remotePort validation

[sivukhin]

I ran govanish linter (it still in the WIP phase) against ssh3 repo and it found a but: compiler eliminated following error check from the binary:

remotePort, err = strconv.Atoi(array[1])
if err != nil {
	return 0, nil, 0, fmt.Errorf("could not convert %s to int: %s", array[1], err)
} else if localPort > 0xFFFF {
	return 0, nil, 0, fmt.Errorf("UDP port too large %d", remotePort)
}

2023/12/25 19:08:30 it seems like your code vanished from compiled binary: func=[parseAddrPort], file=[/home/sivukhin/code/ssh3/cmd/ssh3/main.go], line=[226], snippet:
	return 0, nil, 0, fmt.Errorf("UDP port too large %d", remotePort)

This is a bug, because we need to validation remotePort value instead.

This PR fixes this minor issue.