docs: update and shorten server example (#22583)

docs/2.guide/2.directory-structure/1.server.md

@@ -152,7 +152,10 @@ Server routes can use dynamic parameters within brackets in the file name like `
 **Example:**
 
 ```ts [server/api/hello/[name\\].ts]
-export default defineEventHandler((event) => `Hello, ${event.context.params.name}!`)
+export default defineEventHandler((event) => {
+  const name = getRouterParam(event, 'name')
+  return `Hello, ${name}!`
+})
 ```
 
 You can now universally call this API using `await $fetch('/api/hello/nuxt')` and get `Hello, nuxt!`.