test: use createReadStream instead of ReadStream

This commit updates test-fs-read-stream to use fs.createReadStream
instead of using fs.ReadStream. All other places in this test use
the former.

PR-URL: nodejs#19636
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-fs-read-stream.js

@@ -35,7 +35,7 @@ const rangeFile = fixtures.path('x.txt');
   let paused = false;
   let bytesRead = 0;
 
-  const file = fs.ReadStream(fn);
+  const file = fs.createReadStream(fn);
   const fileSize = fs.statSync(fn).size;
 
   assert.strictEqual(file.bytesRead, 0);