ios: Mark WebStateObserverTest_FailedLoad as flaky.

Bug: 954232
Change-Id: Ib50e4199094ac2bc429bdf51342e11f77e6381c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2369572
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800713}

ios/web/web_state/web_state_observer_inttest.mm

@@ -1961,13 +1961,9 @@ TEST_F(WebStateObserverTest, DownloadNavigation) {
 }
 
 // Tests failed load after the navigation is sucessfully finished.
-// TODO(crbug.com/954232): this test is flaky on device.
-#if TARGET_IPHONE_SIMULATOR
-#define MAYBE_FailedLoad FailedLoad
-#else
-#define MAYBE_FailedLoad FLAKY_FailedLoad
-#endif
-TEST_F(WebStateObserverTest, MAYBE_FailedLoad) {
+// TODO(crbug.com/954232): this test is flaky on device, and as of iOS14
+// simulator as well.
+TEST_F(WebStateObserverTest, FLAKY_FailedLoad) {
   GURL url = test_server_->GetURL("/exabyte_response");
 
   NavigationContext* context = nullptr;