node-web-streams: remove tee shim, use ReadableStream.tee (#54079)

### What?
~The `setTimeout(() => {}, 0)` was used in place of `setImmediate` due to lack of support in the Edge Runtime. This is no longer a problem.~ Not working like I expected. 

`ReadableStream.tee` should be widely supported as well as of [Node 16.5](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/tee#browser_compatibility)

### Why?
Use the platform!

### How?
Use the built-in `ReadableStream.tee()`

packages/next/src/server/app-render/use-flight-response.tsx

@@ -1,6 +1,5 @@
 import type { ClientReferenceManifest } from '../../build/webpack/plugins/flight-manifest-plugin'
 import type { FlightResponseRef } from './flight-response-ref'
-import { readableStreamTee } from '../stream-utils/node-web-streams-helper'
 import { encodeText, decodeText } from '../stream-utils/encode-decode'
 import { htmlEscapeJsonString } from '../htmlescape'
 
@@ -26,7 +25,7 @@ export function useFlightResponse(
     createFromReadableStream,
   } = require(`react-server-dom-webpack/client.edge`)
 
-  const [renderStream, forwardStream] = readableStreamTee(req)
+  const [renderStream, forwardStream] = req.tee()
   const res = createFromReadableStream(renderStream, {
     moduleMap: isEdgeRuntime
       ? clientReferenceManifest.edgeSSRModuleMapping

packages/next/src/server/stream-utils/node-web-streams-helper.ts

@@ -52,29 +52,6 @@ export function cloneTransformStream(source: TransformStream) {
   return clone
 }
 
-export function readableStreamTee<T = any>(
-  readable: ReadableStream<T>
-): [ReadableStream<T>, ReadableStream<T>] {
-  const transformStream = new TransformStream()
-  const transformStream2 = new TransformStream()
-  const writer = transformStream.writable.getWriter()
-  const writer2 = transformStream2.writable.getWriter()
-
-  const reader = readable.getReader()
-  async function read() {
-    const { done, value } = await reader.read()
-    if (done) {
-      await Promise.all([writer.close(), writer2.close()])
-      return
-    }
-    await Promise.all([writer.write(value), writer2.write(value)])
-    await read()
-  }
-  read()
-
-  return [transformStream.readable, transformStream2.readable]
-}
-
 export function chainStreams<T>(
   streams: ReadableStream<T>[]
 ): ReadableStream<T> {