the mqtt topic is automatically set, so no need to expose the property the user - now hiding property in class constructor

Author: gigapod

src/iot/iot_thingspeak/flxIoTThingSpeak.h

@@ -88,6 +88,10 @@ class flxIoTThingSpeak : public flxMQTTESP32SecureCore<flxIoTThingSpeak>, public
 
         flxRegister(deviceList, "Channels", "Comma separated list of <device name>=<channel ID>");
 
+        // The topic is auto-generated -- it needs/uses the channel ID. So, let's hide the topic property it from the
+        // user
+        topic.setHidden(true);
+
         flux.add(this);
     }