docs: change runtime value in example code (vercel#72274)

## Description
[Invalid Page / API Route
Config](https://nextjs.org/docs/messages/invalid-page-config) shows some
examples.
However, runtime examples are same `nodejs` runtime.
Then I add `edge` value instead of duplicate value.

### Improving Documentation

- [x] Run `pnpm prettier-fix` to fix formatting issues before opening
the PR.
- [x] Read the Docs Contribution Guide to ensure your contribution
follows the docs guidelines:
https://nextjs.org/docs/community/contribution-guide

Co-authored-by: Delba de Oliveira <[email protected]>

errors/invalid-page-config.mdx

@@ -86,7 +86,7 @@ export const config = {
   runtime: 'nodejs',
 }
 export const config = {
-  runtime: `nodejs`,
+  runtime: `edge`,
 }
 ```