Enable ScreenTimeControllerTest

The tests used to be flaky. Re-enabling them to check if they are
still flaky after code mauve. (Code mauve did changes to login tests
building blocks)

Bug: 936407
Change-Id: I7dc8102ac6fe7e75c47deb028fb4cf2de0dc631f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1714024Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680454}

chrome/browser/chromeos/child_accounts/screen_time_controller_browsertest.cc

@@ -877,12 +877,6 @@ IN_PROC_BROWSER_TEST_P(ScreenTimeControllerTest, CallObservers) {
       ->RemoveObserver(&observer);
 }
 
-// TODO(crbug.com/936407): Most of this suite is flaky.
-#if !defined(NDEBUG) || defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)
-// Run all ScreenTimeControllerTest with UsageTimeStateNotifier feature enabled
-// and disabled.
-INSTANTIATE_TEST_SUITE_P(DISABLED_, ScreenTimeControllerTest, testing::Bool());
-#else
 INSTANTIATE_TEST_SUITE_P(, ScreenTimeControllerTest, testing::Bool());
-#endif
+
 }  // namespace chromeos