[Kiosk] Reenable previously flaky KioskTest.LaunchAppUserCancel

The test was flaky in the race condition when we were trying to perform
a user exit, while creating a new user.
It is fixed here https://crrev.com/c/2066717.

Bug: 964333
Change-Id: I124c48c1c7d55b69ae9c998a34ffed796207134c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2070410Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744250}

chrome/browser/chromeos/login/kiosk_browsertest.cc

@@ -1021,8 +1021,7 @@ IN_PROC_BROWSER_TEST_F(KioskTest, LaunchAppNetworkPortal) {
   WaitForAppLaunchSuccess();
 }
 
-// TODO(https://crbug.com/964333): Flakily seg faults.
-IN_PROC_BROWSER_TEST_F(KioskTest, DISABLED_LaunchAppUserCancel) {
+IN_PROC_BROWSER_TEST_F(KioskTest, LaunchAppUserCancel) {
   // Make fake_cws_ return empty update response.
   set_test_app_version("");
   OobeScreenWaiter splash_waiter(AppLaunchSplashScreenView::kScreenId);