docs(js): Update Next.js instrumentation instructions (#12532)

Author: chargome

docs/platforms/javascript/guides/nextjs/manual-setup.mdx

@@ -156,8 +156,12 @@ We recommend you include your DSN directly in these three files. Alternatively y
 
 While the client initialization code will be injected into your application's client bundle by `withSentryConfig` which we set up earlier,
 the configuration for the server and edge runtime needs to be imported from a [Next.js Instrumentation file](https://nextjs.org/docs/app/building-your-application/optimizing/instrumentation).
-To set up this file, enable the Next.js instrumentation hook by setting the [`experimental.instrumentationHook`](https://nextjs.org/docs/app/api-reference/next-config-js/instrumentationHook) to `true` in your `next.config.js`.
-Then add a `instrumentation.ts` file to the root directory of your Next.js application (or inside the `src` folder if you're using one) and add the following content:
+
+<Alert>
+For Next.js versions `<15` enable the Next.js instrumentation hook by setting the [`experimental.instrumentationHook`](https://nextjs.org/docs/14/pages/api-reference/next-config-js/instrumentationHook) to `true` in your `next.config.js`.
+</Alert>
+
+Add a `instrumentation.ts` file to the root directory of your Next.js application (or inside the `src` folder if you're using one) and add the following content:
 
 ```javascript {filename:instrumentation.(js|ts)}
 export async function register() {
@@ -171,6 +175,7 @@ export async function register() {
 }
 ```
 
+
 Make sure that the `import` statements point to your newly created `sentry.server.config.(js|ts)` and `sentry.edge.config.(js|ts)` files.
 
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