[iOS] Disabling flaky sync tests

Disabling EarlGrey tests from SigninInteractionControllerTestCase:
 + testSignInSwitchAccountsAndKeepDataSeparate
 + testSignInSwitchAccountsAndImportData
 + testSignInSwitchManagedAccount

Those tests seem to trigger an issue in the sync code when doing enable
disable enable too fast.

Bug: 854446
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I76d10d272297e91650dbe91ef7acee500eac6c75
Reviewed-on: https://chromium-review.googlesource.com/1107881Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568843}

ios/chrome/browser/ui/signin_interaction/signin_interaction_controller_egtest.mm

@@ -99,7 +99,8 @@ void WaitForMatcher(id<GREYMatcher> matcher) {
 
 // Tests signing in with one account, switching sync account to a second and
 // choosing to keep the browsing data separate during the switch.
-- (void)testSignInSwitchAccountsAndKeepDataSeparate {
+// TODO(crbug.com/854446): Enable after fixing.
+- (void)DISABLED_testSignInSwitchAccountsAndKeepDataSeparate {
   // Set up the fake identities.
   ios::FakeChromeIdentityService* identity_service =
       ios::FakeChromeIdentityService::GetInstanceFromChromeProvider();
@@ -136,7 +137,8 @@ void WaitForMatcher(id<GREYMatcher> matcher) {
 
 // Tests signing in with one account, switching sync account to a second and
 // choosing to import the browsing data during the switch.
-- (void)testSignInSwitchAccountsAndImportData {
+// TODO(crbug.com/854446): Enable after fixing.
+- (void)DISABLED_testSignInSwitchAccountsAndImportData {
   // Set up the fake identities.
   ios::FakeChromeIdentityService* identity_service =
       ios::FakeChromeIdentityService::GetInstanceFromChromeProvider();
@@ -174,7 +176,8 @@ void WaitForMatcher(id<GREYMatcher> matcher) {
 
 // Tests that switching from a managed account to a non-managed account works
 // correctly and displays the expected warnings.
-- (void)testSignInSwitchManagedAccount {
+// TODO(crbug.com/854446): Enable after fixing.
+- (void)DISABLED_testSignInSwitchManagedAccount {
   // Set up the fake identities.
   ios::FakeChromeIdentityService* identity_service =
       ios::FakeChromeIdentityService::GetInstanceFromChromeProvider();