fix: correctly mention generateStaticParams in error (#42524)

Fixes #42517

Not sure if it warrants a test case, but let me know if I should add one.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

packages/next/build/utils.ts

@@ -828,13 +828,15 @@ export async function buildStaticPaths({
   configFileName,
   locales,
   defaultLocale,
+  appDir,
 }: {
   page: string
   getStaticPaths?: GetStaticPaths
   staticPathsResult?: UnwrapPromise<ReturnType<GetStaticPaths>>
   configFileName: string
   locales?: string[]
   defaultLocale?: string
+  appDir?: boolean
 }): Promise<
   Omit<UnwrapPromise<ReturnType<GetStaticPaths>>, 'paths'> & {
     paths: string[]
@@ -982,7 +984,9 @@ export async function buildStaticPaths({
           throw new Error(
             `A required parameter (${validParamKey}) was not provided as ${
               repeat ? 'an array' : 'a string'
-            } in getStaticPaths for ${page}`
+            } in ${
+              appDir ? 'generateStaticParams' : 'getStaticPaths'
+            } for ${page}`
           )
         }
         let replaced = `[${repeat ? '...' : ''}${validParamKey}]`
@@ -1193,6 +1197,7 @@ export async function buildAppStaticPaths({
       },
       page,
       configFileName,
+      appDir: true,
     })
   }
 }