Remove unnecessary type reference in Vitest example

[michaeloliverx]

Documentation / Examples

• Make sure the linting passes by running pnpm lint
• The examples guidelines are followed from our contributing doc

---

The Vitest docs state that /// <reference types="vitest" /> is only required when importing defineConfig from vite.

using defineConfig from vitest/config you should follow this:

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    // ...
  },
})

[ijjk]

Thanks!