Disable KioskTest.LaunchAppUserCancel for flakiness

This was recently re-enabled as one source of flakiness was fixed, but
this test is still flaky for another reason; it seg faults in
chromeos::UserSessionManager::InitializeBrowser. We disable this test
again.

Tbr: alemate@chromium.org
Bug: 961607, 964333
Change-Id: I3bc48798afabfbe004173b5faf9ad810be5bdff7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617377Reviewed-by: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660849}

chrome/browser/chromeos/login/kiosk_browsertest.cc

@@ -1033,7 +1033,8 @@ 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);