remove the Wi-Fi sniffer template

[zhakk-harn]

Why

The template does way more than what is advertised and it's already a default example provided with the standard libraries of ESP32 and ESP8266

On one end I'm tempted to say "we should now find a way to reference these useful examples here" but but on the other end I'm thinking :

1. it should be common knowledge for people used to ESP boards
2. or a mention at the beginning of an ESP32 course for the beginners (or at least in a troubleshooting section "which networks is my board actually seeing?".

any thoughts @b2renger ?