chore: restores removed tests (#39452)

### 📖 What's in there?

As part of the 4 hands work done in #39397, we accidentally removed a describe for middleware "using a single matcher with i18n" (and no base path nor trailing slash).

This PR restores it.

### 🧪 How to test?

```
pnpm testheadless --testPathPattern middleware-matcher
```

### 🆙 Note to reviewers

There's only a couple lines with meaningful change in this PR. Hide whitespaces in github's diff screen to find it more easily: https://github.com/vercel/next.js/pull/39452/files?diff=split&w=1

test/e2e/middleware-matcher/index.test.ts

@@ -322,14 +322,15 @@ describe('using root matcher', () => {
   })
 })
 
-describe.each([{ title: ' and trailingSlash', trailingSlash: true }])(
-  'using a single matcher with i18n$title',
-  ({ trailingSlash }) => {
-    let next: NextInstance
-    beforeAll(async () => {
-      next = await createNext({
-        files: {
-          'pages/index.js': `
+describe.each([
+  { title: '' },
+  { title: ' and trailingSlash', trailingSlash: true },
+])('using a single matcher with i18n$title', ({ trailingSlash }) => {
+  let next: NextInstance
+  beforeAll(async () => {
+    next = await createNext({
+      files: {
+        'pages/index.js': `
           export default function Page({ message }) {
             return <div>
               <p>{message}</p>
@@ -339,7 +340,7 @@ describe.each([{ title: ' and trailingSlash', trailingSlash: true }])(
             props: { message: \`(\${locale}) Hello from /\` }
           })
         `,
-          'pages/[...route].js': `
+        'pages/[...route].js': `
           export default function Page({ message }) {
             return <div>
               <p>catchall page</p>
@@ -350,7 +351,7 @@ describe.each([{ title: ' and trailingSlash', trailingSlash: true }])(
             props: { message: \`(\${locale}) Hello from /\` + params.route.join("/") }
           })
         `,
-          'middleware.js': `
+        'middleware.js': `
           import { NextResponse } from 'next/server'
           export const config = { matcher: '/' };
           export default (req) => {
@@ -359,7 +360,7 @@ describe.each([{ title: ' and trailingSlash', trailingSlash: true }])(
             return res;
           }
         `,
-          'next.config.js': `
+        'next.config.js': `
           module.exports = {
             ${trailingSlash ? 'trailingSlash: true,' : ''}
             i18n: {
@@ -369,59 +370,58 @@ describe.each([{ title: ' and trailingSlash', trailingSlash: true }])(
             }
           }
         `,
-        },
-        dependencies: {},
-      })
+      },
+      dependencies: {},
     })
-    afterAll(() => next.destroy())
+  })
+  afterAll(() => next.destroy())
 
-    it(`adds the header for a matched path`, async () => {
-      const res1 = await fetchViaHTTP(next.url, `/`)
-      expect(await res1.text()).toContain(`(en) Hello from /`)
-      expect(res1.headers.get('X-From-Middleware')).toBe('true')
-      const res2 = await fetchViaHTTP(next.url, `/es`)
-      expect(await res2.text()).toContain(`(es) Hello from /`)
-      expect(res2.headers.get('X-From-Middleware')).toBe('true')
-    })
+  it(`adds the header for a matched path`, async () => {
+    const res1 = await fetchViaHTTP(next.url, `/`)
+    expect(await res1.text()).toContain(`(en) Hello from /`)
+    expect(res1.headers.get('X-From-Middleware')).toBe('true')
+    const res2 = await fetchViaHTTP(next.url, `/es`)
+    expect(await res2.text()).toContain(`(es) Hello from /`)
+    expect(res2.headers.get('X-From-Middleware')).toBe('true')
+  })
 
-    it('adds the header for a mathed root path with /index', async () => {
-      const res1 = await fetchViaHTTP(next.url, `/index`)
-      expect(await res1.text()).toContain(`(en) Hello from /`)
-      expect(res1.headers.get('X-From-Middleware')).toBe('true')
-      const res2 = await fetchViaHTTP(next.url, `/es/index`)
-      expect(await res2.text()).toContain(`(es) Hello from /`)
-      expect(res2.headers.get('X-From-Middleware')).toBe('true')
-    })
+  it('adds the header for a mathed root path with /index', async () => {
+    const res1 = await fetchViaHTTP(next.url, `/index`)
+    expect(await res1.text()).toContain(`(en) Hello from /`)
+    expect(res1.headers.get('X-From-Middleware')).toBe('true')
+    const res2 = await fetchViaHTTP(next.url, `/es/index`)
+    expect(await res2.text()).toContain(`(es) Hello from /`)
+    expect(res2.headers.get('X-From-Middleware')).toBe('true')
+  })
 
-    it(`adds the headers for a matched data path`, async () => {
-      const res1 = await fetchViaHTTP(
-        next.url,
-        `/_next/data/${next.buildId}/en.json`,
-        undefined,
-        { headers: { 'x-nextjs-data': '1' } }
-      )
-      expect(await res1.json()).toMatchObject({
-        pageProps: { message: `(en) Hello from /` },
-      })
-      expect(res1.headers.get('X-From-Middleware')).toBe('true')
-      const res2 = await fetchViaHTTP(
-        next.url,
-        `/_next/data/${next.buildId}/es.json`,
-        undefined
-      )
-      expect(await res2.json()).toMatchObject({
-        pageProps: { message: `(es) Hello from /` },
-      })
-      expect(res2.headers.get('X-From-Middleware')).toBe('true')
+  it(`adds the headers for a matched data path`, async () => {
+    const res1 = await fetchViaHTTP(
+      next.url,
+      `/_next/data/${next.buildId}/en.json`,
+      undefined,
+      { headers: { 'x-nextjs-data': '1' } }
+    )
+    expect(await res1.json()).toMatchObject({
+      pageProps: { message: `(en) Hello from /` },
     })
-
-    it(`does not add the header for an unmatched path`, async () => {
-      const response = await fetchViaHTTP(next.url, `/about/me`)
-      expect(await response.text()).toContain('Hello from /about/me')
-      expect(response.headers.get('X-From-Middleware')).toBeNull()
+    expect(res1.headers.get('X-From-Middleware')).toBe('true')
+    const res2 = await fetchViaHTTP(
+      next.url,
+      `/_next/data/${next.buildId}/es.json`,
+      undefined
+    )
+    expect(await res2.json()).toMatchObject({
+      pageProps: { message: `(es) Hello from /` },
     })
-  }
-)
+    expect(res2.headers.get('X-From-Middleware')).toBe('true')
+  })
+
+  it(`does not add the header for an unmatched path`, async () => {
+    const response = await fetchViaHTTP(next.url, `/about/me`)
+    expect(await response.text()).toContain('Hello from /about/me')
+    expect(response.headers.get('X-From-Middleware')).toBeNull()
+  })
+})
 
 describe.each([
   { title: '' },