Revert "[Kiosk] Reenable previously flaky KioskTest.LaunchAppUserCancel"

This reverts commit 3d6903ce.

Reason for revert: <INSERT REASONING HERE>
KioskTest.LaunchAppUserCancel is still flaky on
Builder linux-chromeos-dbg
https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg


Original change's description:
> [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/+/2070410
> Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
> Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#744250}

TBR=rsorokin@chromium.org,apotapchuk@chromium.org

Change-Id: I091490b85c4da75908837900682ce6dd12ee2c7d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 964333
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2072133Reviewed-by: Lan Wei <lanwei@chromium.org>
Commit-Queue: Lan Wei <lanwei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744299}

chrome/browser/chromeos/login/kiosk_browsertest.cc

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