test: don't use expose internals in test-http-outgoing-buffer.js

PR-URL: #59219
Reviewed-By: Zeyu "Alex" Yang <himself65@outlook.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>

Author: nektro

test/parallel/test-http-outgoing-buffer.js

@@ -1,8 +1,7 @@
-// Flags: --expose-internals
 'use strict';
 require('../common');
 const assert = require('assert');
-const { getDefaultHighWaterMark } = require('internal/streams/state');
+const { getDefaultHighWaterMark } = require('stream');
 
 const http = require('http');
 const OutgoingMessage = http.OutgoingMessage;