Try to resolve flaky ExtensionRequestNotificationTest.NoExtension

The test is timeout on trybots which is likely caused by the
RunUntilIdle() function which is put here just in case. Trying to solve
the timeout issue by removing the function.

Bug: 1137094
Change-Id: I4e48b937901ffa23f2daff6c41050eaa7b9f7f5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615324Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841482}

chrome/browser/enterprise/reporting/extension_request/extension_request_notification_unittest.cc

@@ -81,7 +81,6 @@ TEST_P(ExtensionRequestNotificationTest, NoExtension) {
 #else
   request_notification.Show(base::BindOnce(&OnNotificationClosed, false));
 #endif
-  task_environment()->RunUntilIdle();
   EXPECT_FALSE(GetNotification().has_value());
 }