fs: close file descriptor of promisified truncate

Original PR:
  PR-URL: #28858
  Reviewed-By: Rich Trott <rtrott@gmail.com>
  Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

PR-URL: #34239
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

lib/internal/fs/promises.js

@@ -305,7 +305,8 @@ async function rename(oldPath, newPath) {
 }
 
 async function truncate(path, len = 0) {
-  return ftruncate(await open(path, 'r+'), len);
+  const fd = await open(path, 'r+');
+  return ftruncate(fd, len).finally(fd.close.bind(fd));
 }
 
 async function ftruncate(handle, len = 0) {