Update 06-bundle-analyzer.mdx (#64740)

The[ existing code
example](https://nextjs.org/docs/app/building-your-application/optimizing/bundle-analyzer)
generates the following warning when using `--turbo` in the current
latest version of NextJS (14.2.2):

⚠ Webpack is configured while Turbopack is not, which may cause
problems.
 ⚠ See instructions if you need to configure Turbopack:
  https://nextjs.org/docs/app/api-reference/next-config-js/turbo

This modification ensures that the bundle analyzer is only applied when
the user intends to generate a report.

Fixes # #64739

---------

Co-authored-by: Lee Robinson <me@leerob.io>
Co-authored-by: Maxim Svetlakov <maxim@ebookapplications.com>
Co-authored-by: JJ Kasper <jj@jjsweb.site>

docs/02-app/01-building-your-application/06-optimizing/06-bundle-analyzer.mdx

@@ -24,14 +24,13 @@ pnpm add @next/bundle-analyzer
 Then, add the bundle analyzer's settings to your `next.config.js`.
 
 ```js filename="next.config.js"
-const withBundleAnalyzer = require('@next/bundle-analyzer')({
-  enabled: process.env.ANALYZE === 'true',
-})
-
 /** @type {import('next').NextConfig} */
 const nextConfig = {}
 
-module.exports = withBundleAnalyzer(nextConfig)
+const withBundleAnalyzer = require('@next/bundle-analyzer')()
+
+module.exports =
+  process.env.ANALYZE === 'true' ? withBundleAnalyzer(nextConfig) : nextConfig
 ```
 
 ## Analyzing your bundles