[DISC] Removal of openHAB specific MQTT discovery patch (#2153)

Removal of openHAB specific MQTT discovery patch "ohdisc", as it is no longer required with openHAB 4.3 and later, and with openHAB before 4.3 MQTT discovery never was fully implemented anyway.

main/User_config.h

@@ -670,7 +670,6 @@ struct SYSConfig_s {
   bool blufi; // if true the gateway will be accesible with blufi
   bool offline;
   bool discovery; // HA discovery convention
-  bool ohdiscovery; // OH discovery specificities
 #ifdef LED_ADDRESSABLE
   int rgbbrightness; // brightness of the RGB LED
 #endif