Remove node fetch polyfill from base server

Author: huozhi

packages/next/server/base-server.ts

@@ -57,7 +57,6 @@ import { execOnce } from '../shared/lib/utils'
 import { isBlockedPage, isBot } from './utils'
 import RenderResult from './render-result'
 import { loadEnvConfig } from '@next/env'
-import './node-polyfill-fetch'
 import { PagesManifest } from '../build/webpack/plugins/pages-manifest-plugin'
 import { removePathTrailingSlash } from '../client/normalize-trailing-slash'
 import getRouteFromAssetPath from '../shared/lib/router/utils/get-route-from-asset-path'