Update examples

examples/MqttClient/MqttClient.ino

@@ -68,9 +68,12 @@ void setup() {
   delay(3000);
 
   // Restart takes quite some time
-  // You can skip it in many cases
+  // To skip it, call init() instead of restart()
   modem.restart();
 
+  // Unlock your SIM card with a PIN
+  //modem.simUnlock("1234");
+
   Serial.print("Waiting for network...");
   if (!modem.waitForNetwork()) {
     Serial.println(" fail");