Remove FLAKY_ prefix from FailedLoad test.

The root cause should be fixed in crrev.com/c/1553501 . This CL simply
enables the test.

Bug: 845879
Change-Id: I396396ef661501855a1f3082449f8a1caa246eaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1555251Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#648715}

ios/web/web_state/web_state_observer_inttest.mm

@@ -2034,13 +2034,7 @@ TEST_P(WebStateObserverTest, DownloadNavigation) {
 }
 
 // Tests failed load after the navigation is sucessfully finished.
-// TODO(crbug.com/845879): test is flaky (probably since crrev.com/1056203).
-#if TARGET_IPHONE_SIMULATOR
-#define MAYBE_FailedLoad FailedLoad
-#else
-#define MAYBE_FailedLoad FLAKY_FailedLoad
-#endif
-TEST_P(WebStateObserverTest, FLAKY_FailedLoad) {
+TEST_P(WebStateObserverTest, FailedLoad) {
   GURL url = test_server_->GetURL("/exabyte_response");
 
   NavigationContext* context = nullptr;