docs: update code for functions example

Author: NathanFlurry

site/src/content/docs/functions.mdx

@@ -21,7 +21,7 @@ cd my-rivet-function
 
 # Setup NPM
 npm init -y
-npm install hono
+npm install hono@4 @hono/node-server@1
 ```
 
 Add the following files: 
@@ -39,31 +39,25 @@ Add the following files:
 ```
 
 ```javascript {{ "title": "index.js" }}
-const { Hono } = require('hono');
-const { serve } = require('hono/node-server');
+import { Hono } from "hono";
+import { serve } from "@hono/node-server";
+
 const app = new Hono();
 const port = process.env.PORT_HTTP || 8080;
 
-app.get('/', (c) => {
-  return c.text('Hello from Rivet Functions!');
-});
-
-app.get('/api/data', (c) => {
-  return c.json({
-    message: 'This is data from your Rivet Function',
-    timestamp: new Date().toISOString()
-  });
+app.get("/", (c) => {
+	return c.text("Hello from Rivet Functions!");
 });
 
 console.log(`Server running on port ${port}`);
 serve({
-  fetch: app.fetch,
-  port
+	fetch: app.fetch,
+	port,
 });
 ```
 
 ```dockerfile {{ "title": "Dockerfile" }}
-FROM node:18-alpine
+FROM node:22-alpine
 
 RUN addgroup -S rivet && adduser -S rivet -G rivet
 
@@ -76,8 +70,6 @@ COPY . .
 RUN chown -R rivet:rivet /app
 USER rivet
 
-EXPOSE 8080
-
 CMD ["node", "index.js"]
 ```