Fix: IE10 bug - DOCTYPE, IE=Edge, let -> var

src/web/module/maestro_upgrade.html

@@ -1,6 +1,6 @@
 <script>
 
-let registeredAccountType = -1;
+var registeredAccountType = -1;
 
 
 $(document).ready(function() {
@@ -147,7 +147,7 @@ function setCardConent(cardNo, cardType) {
 
 function upgradeMaestroInfo(accountType) {
 	console.log("upgrade to " + accountType);
-	let upgradeAccountType = accountType;
+	var upgradeAccountType = accountType;
 
 	sendRequestServer(	//url, sendParams, onSuccess, onFail, isDebugMode);
 		"./../server/maestro/request_upgrade_maestro.php",