[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.

docs/integrate/openhab3.md

@@ -76,13 +76,6 @@ Or use another upload method from the Upload section that requires credentials b
 
 You should see the gateway connected to your broker by checking with an MQTT client like MQTT Explorer.
 
-To make the auto discovery compatible with OpenHAB you have to send the following command with a retain flag.
-
-`mosquitto_pub -t "home/OpenMQTTGateway/commands/MQTTtoSYS/config" -m '{"ohdisc":true}'`
-
-You can also activate OpenHAB auto discovery by adding the gateway as a Thing, Model, and switching the button to ON. The name of the channel to add is "SYS: OpenHAB discovery".
-Once activated restart OpenMQTTGateway.
-
 ## Adding the things
 1. From the Administration click on "Things" under "Settings", you should see a number in the INBOX button