Update next-custom-transforms test fixtures

To test "next/root-params" instead of "unstable_rootParams"

Author: devjiwonchoi

crates/next-custom-transforms/tests/errors/react-server-components/client-graph/root-params/input.js

@@ -6,7 +6,7 @@
  * This is a comment.
  */
 
-import { unstable_rootParams } from 'next/server'
+import { lang } from 'next/root-params'
 
 export default function () {
   return null

crates/next-custom-transforms/tests/errors/react-server-components/client-graph/root-params/output.js

@@ -2,7 +2,7 @@
 'use strict';
 /**
  * This is a comment.
- */ import { unstable_rootParams } from 'next/server';
+ */ import { lang } from 'next/root-params';
 export default function() {
     return null;
 }

crates/next-custom-transforms/tests/errors/react-server-components/client-graph/root-params/output.stderr

@@ -1,9 +1,9 @@
-  x You're importing a component that needs "unstable_rootParams". That only works in a Server Component which is not supported in the pages/ directory. Read more: https://nextjs.org/docs/app/
-  | building-your-application/rendering/server-components
+  x You're importing a component that needs "next/root-params". That only works in a Server Component which is not supported in the pages/ directory. Read more: https://nextjs.org/docs/app/building-
+  | your-application/rendering/server-components
   | 
   | 
    ,-[input.js:9:1]
  8 | 
- 9 | import { unstable_rootParams } from 'next/server'
-   :          ^^^^^^^^^^^^^^^^^^^
+ 9 | import { lang } from 'next/root-params'
+   : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    `----