Update response message in Lambda handler

The text returned by the Lambda handler's response has been updated for clarity. This change enhances the demonstrative impact of the message, improving user experience.

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;
 };