🔥 Remove hardcoded keepalive - fix #301 (#314)

Remove hardcoded KeepAlive for MQTT connection.
Default value of 15sec is already present in AsyncMQTT library

src/Homie/Boot/BootNormal.cpp

@@ -662,7 +662,7 @@ void BootNormal::setup() {
   Interface::get().getMqttClient().onPublish(std::bind(&BootNormal::_onMqttPublish, this, std::placeholders::_1));
 
   Interface::get().getMqttClient().setServer(Interface::get().getConfig().get().mqtt.server.host, Interface::get().getConfig().get().mqtt.server.port);
-  Interface::get().getMqttClient().setKeepAlive(10).setMaxTopicLength(MAX_MQTT_TOPIC_LENGTH);
+  Interface::get().getMqttClient().setMaxTopicLength(MAX_MQTT_TOPIC_LENGTH);
   _mqttClientId = std::unique_ptr<char[]>(new char[strlen(Interface::get().brand) + 1 + strlen(Interface::get().getConfig().get().deviceId) + 1]);
   strcpy(_mqttClientId.get(), Interface::get().brand);
   strcat_P(_mqttClientId.get(), PSTR("-"));