update esp mqtt library

lib/espMqttClient/examples/simple-esp8266/simple-esp8266.ino

@@ -1,5 +1,4 @@
 #include <ESP8266WiFi.h>
-#include <Ticker.h>
 
 #include <espMqttClient.h>
 
@@ -32,11 +31,13 @@ void connectToMqtt() {
 }
 
 void onWiFiConnect(const WiFiEventStationModeGotIP& event) {
+  (void) event;
   Serial.println("Connected to Wi-Fi.");
   connectToMqtt();
 }
 
 void onWiFiDisconnect(const WiFiEventStationModeDisconnected& event) {
+  (void) event;
   Serial.println("Disconnected from Wi-Fi.");
 }
 
@@ -83,6 +84,7 @@ void onMqttUnsubscribe(uint16_t packetId) {
 }
 
 void onMqttMessage(const espMqttClientTypes::MessageProperties& properties, const char* topic, const uint8_t* payload, size_t len, size_t index, size_t total) {
+  (void) payload;
   Serial.println("Publish received.");
   Serial.print("  topic: ");
   Serial.println(topic);