BUGFIX: Removing double default for MQTT

ampel-firmware/web_config.cpp

@@ -100,7 +100,7 @@ namespace web_config {
 
   IntTParameter<uint16_t> mqttIntervalParam =
       Builder<IntTParameter<uint16_t>>("mqtt_interval").label("MQTT interval").defaultValue(MQTT_SENDING_INTERVAL).min(
-          0).step(1).defaultValue(300).placeholder("[s]").build();
+          0).step(1).placeholder("[s]").build();
 
   CheckboxTParameter mqttEncryptionParam =
       Builder<CheckboxTParameter>("mqtt_encryption").label("Encrypt MQTT?").defaultValue(MQTT_ENCRYPTED).build();