Fix middleware documentation (#48876)

In the actual documentation, `value` does not exist. I removed `value`
and work correctly

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

docs/02-app/01-building-your-application/01-routing/11-middleware.mdx

@@ -140,8 +140,8 @@ import type { NextRequest } from 'next/server'
 export function middleware(request: NextRequest) {
   // Assume a "Cookie:nextjs=fast" header to be present on the incoming request
   // Getting cookies from the request using the `RequestCookies` API
-  let cookie = request.cookies.get('nextjs')?.value
-  console.log(cookie) // => 'fast'
+  let cookie = request.cookies.get('nextjs')
+  console.log(cookie) // => { name: 'nextjs', value: 'fast', Path: '/' }
   const allCookies = request.cookies.getAll()
   console.log(allCookies) // => [{ name: 'nextjs', value: 'fast' }]