[mqtt] improve documentation (openhab#9541)

Signed-off-by: Jan N. Klug <[email protected]>

bundles/org.openhab.binding.mqtt/README.md

@@ -6,8 +6,7 @@
 MQTT is a server/client architecture.
 
 A server, also called broker is not provided within this binding.
-You can use any of the freely available MQTT Brokers like [Mosquitto](https://mosquitto.org/)
-or [Moquette](https://moquette-io.github.io/moquette/) or install the [included Moquette broker](https://www.openhab.org/addons/integrations/mqttembeddedbroker/) as add-on.
+You can use any of the freely available MQTT Brokers like [Mosquitto](https://mosquitto.org/).
 
 This particular binding allows to configure connections to brokers via openHAB Things.
 This binding does NOT allow you to link Channels to MQTT topics or perform auto-discovery of available
@@ -69,8 +68,3 @@ Configuration parameters are:
 
 * __stateTopic__: This channel will trigger on this MQTT topic. This topic can contain wildcards like + and # for example "all/in/#" or "sensors/+/config".
 * __payload__: An optional condition on the value of the MQTT topic that must match before this channel is triggered.
-
-## Legacy MQTT1-Binding
-
-This binding is not supposed to run in parallel to the old mqtt1-binding.
-Please uninstall the old binding before installing this binding.