Update greeting message in lambda function

The change in this commit updates the greeting message returned by the Lambda function. The update only involves adding an extra exclamation mark to the message, making it a bit more enthusiastic.

demo/lambda/src/app.js

@@ -1,7 +1,7 @@
 exports.handler = async (event) => {
     const response = {
         statusCode: 200,
-        body: JSON.stringify('Hello from Lambda!')
+        body: JSON.stringify('Hello from Lambda!!')
     };
     return response;
 };