Spurious triggers of hardcoded Udp -> EthernetUdp migration error enhancement causes confusion

Arduino often calls static methods like Wifi.begin(). When reading the documentation on [Arduino's WiFiSendReceiveUDPString page](https://www.arduino.cc/en/Tutorial/WiFiSendReceiveUDPString), if you don't pay attention to the declaration "WiFiUDP Udp" you will assume that the "Udp" in the code samples is a static class.

Not a problem though, if you don't declare "WiFiUDP Udp", you will just get an error that variable is missing, right? No. You get the error that Udp was renamed to EthernetUdp. And now you're off on a wild goose chase trying to figure out what EthernetUdp is and where to get that library.

My suggestion is either change the documentation and set "WiFiUDP udp", making it obvious that "udp" is a variable, or remove the error that says Udp has been changed to EthernetUdp and make it clear that the variable is not declared.

Review the linked WiFiSendReceiveUDPString documentation and locate the Arduino IDE diagnostic that rewrites `Udp` to `EthernetUdp`. Decide between clarifying the documentation with `udp` or correcting the diagnostic, then verify that an undeclared variable produces a clear missing-variable error.

Written by the indexing model from the issue text.