NativeIO: Added a missing await in the WPT for rename.

Bug: 1097126
Change-Id: I3775c97543b4603e910f5cf4ec1f5a7207fd7276
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308420Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Richard Stotz <rstz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790382}

third_party/blink/web_tests/external/wpt/native-io/rename_async_failure_handling.tentative.https.any.js

@@ -93,8 +93,8 @@ promise_test(async testCase => {
   closed_file.close();
   const opened_file = await nativeIO.open('opened_file');
   testCase.add_cleanup(async () => {
-    closed_file.close();
-    opened_file.close();
+    await closed_file.close();
+    await opened_file.close();
     await nativeIO.delete('closed_file');
     await nativeIO.delete('opened_file');
   });