Update platform-includes/sourcemaps/overview/javascript.nextjs.mdx

Co-authored-by: Sergiy Dybskiy <[email protected]>

Author: sfanahata

platform-includes/sourcemaps/overview/javascript.nextjs.mdx

@@ -32,7 +32,7 @@ module.exports = withSentryConfig(
 
 Configure source map behavior using the [source maps options](/platforms/javascript/guides/nextjs/configuration/build/#source-maps-options) in your Next.js config:
 
-```javascript {filename:next.config.js}
+```javascript {11-16} {filename:next.config.js}
 const { withSentryConfig } = require("@sentry/nextjs");
 
 module.exports = withSentryConfig(