fix: root key is required

Author: chronark

apps/docs/libraries/ts/nextjs.mdx

@@ -50,8 +50,6 @@ export const POST = withUnkey(
 );
 ```
 
-That's it! Since this is just handling key verification, there's no need to specify a root key as an environment variable.
-
 If you want to customize how `withUnkey` processes incoming requests, you can do so as follows:
 
 ### `getKey`