[BOARDS] Remove Arduino boards (#1929)

docs/setitup/rf.md

@@ -32,7 +32,6 @@ Heltec LORA V3 is not compatible with RTL_433 library as it is based on an SX126
 ### SRX STX Pinout
 |Board| Receiver Pin| Emitter Pin|
 |-|:-:|:-:|
-|Arduino UNO|D3|D4|
 |ESP8266|D2/**D3**/D1/D8|**RX**/D2|
 |ESP32|**27**/26|12|
 |RF BRIDGE|-|-|
@@ -65,9 +64,6 @@ With SRX882 some users reported that D3 is not working use D1 instead in this ca
 
 ![Addon_RF](../img/OpenMQTTgateway_ESP8266_Addon_RF.png)
 
-## Arduino Hardware setup
-![RF](../img/OpenMQTTgateway_Arduino_Addon_RF.png)
-
 ## SONOFF RF Bridge Hardware setup
 Per default there is no need on modifying the RF Bridge hardware, unless you don't want to use the provided RF controller (EFM8BB1). Indeed if you want to extend the protocols supported by the bridge you can [bypass this controller](https://github.com/xoseperez/espurna/wiki/Hardware-Itead-Sonoff-RF-Bridge---Direct-Hack) and use the ESP8255 capacities to decode RF Signal.
 The RF processing can be achieved after the modification by either RF, RF2 or Pilight gateways.