Mention app dir in TS setup tip (#70337)

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### What?

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### What?

Update the tip to also mention `app` directory when setting up
TypeScript.

### Why?

The user may be using App Router instead of Pages Router (or both).

### How?

---------

Co-authored-by: JJ Kasper <jj@jjsweb.site>

packages/next/src/lib/typescript/missingDependencyError.ts

@@ -18,7 +18,7 @@ export function missingDepsError(
     bold(
       'If you are not trying to use TypeScript, please remove the ' +
         cyan('tsconfig.json') +
-        ' file from your package root (and any TypeScript files in your pages directory).'
+        ' file from your package root (and any TypeScript files in your app and pages directories).'
     )
 
   throw new FatalError(

packages/next/src/lib/verify-typescript-setup.ts

@@ -87,7 +87,7 @@ export async function verifyTypeScriptSetup({
           bold(
             'If you are not trying to use TypeScript, please remove the ' +
               cyan('tsconfig.json') +
-              ' file from your package root (and any TypeScript files in your pages directory).'
+              ' file from your package root (and any TypeScript files in your app and pages directories).'
           ) +
           '\n'
       )