Reenable testBadgedReadingListFeatureShouldShow.

Reenable this test since flake seems to have been fixed on FYI bots.

Bug: 789943
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I184607d3fc25206409c0786d81583c49a9f8471a
Reviewed-on: https://chromium-review.googlesource.com/807166Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Gregory Chatzinoff <gchatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521764}

ios/chrome/browser/feature_engagement/feature_engagement_egtest.mm

@@ -89,9 +89,7 @@ void EnableBadgedReadingListTriggering(
 
 // Verifies that the Badged Reading List feature shows when triggering
 // conditions are met.
-// TODO(crbug.com/789943): This test is flaky on devices. Reenable it once it is
-// fixed.
-- (void)FLAKY_testBadgedReadingListFeatureShouldShow {
+- (void)testBadgedReadingListFeatureShouldShow {
   base::test::ScopedFeatureList scoped_feature_list;
 
   EnableBadgedReadingListTriggering(scoped_feature_list);