Disconnecting will not release Socket in W5500

[tarnak]

Hi,

I've found an problem when using your library on rp2040 and W5500. As this hardware has only 8 sockets available, after 8 connections/disconnections you will be not able to connect until Socket will timeout itself.
I'm not sure is this issue in W5500 itself or in Ethernet library 2.0.1 which I'm using.

I've found an solution, you need to uncomment deletion of tcpclient in ModbusTCPTemplate.h

`
template <class SERVER, class CLIENT>
void ModbusTCPTemplate<SERVER, CLIENT>::cleanupConnections()

template <class SERVER, class CLIENT>
bool ModbusTCPTemplate<SERVER, CLIENT>::disconnect(IPAddress ip)
`
Seems like stop() is not working well for W5500.

Thanks and keep such a great job, sir.