Revert "Sheriff: Disable tests in ExistingUserControllerActiveDirectoryTest"

This reverts commit bfaedb07.

Reason for revert: I think I've found the culprit CL that caused these test failures in the first place (https://chromium-review.googlesource.com/c/chromium/src/+/2537580), so I'm re-enabling these tests to see if they still fail.

See https://bugs.chromium.org/p/chromium/issues/detail?id=1148771#c3 for more details of the investigation.

Original change's description:
> Sheriff: Disable tests in ExistingUserControllerActiveDirectoryTest
>
> Bug: 1148771
> Change-Id: I676dd86028dbca3f39661aa2b35202facf880281
> Tbr: alemate@chromium.org
> No-Try: True
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2536978
> Reviewed-by: Adithya Srinivasan <adithyas@chromium.org>
> Commit-Queue: Adithya Srinivasan <adithyas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#827245}

TBR=alemate@chromium.org,adithyas@chromium.org

Change-Id: Id51b3e6102219db51af7dc030d9e8256838de7c4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1148771
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537581Reviewed-by: Scott Little <sclittle@chromium.org>
Commit-Queue: Scott Little <sclittle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827324}

chrome/browser/chromeos/login/existing_user_controller_browsertest.cc

@@ -986,17 +986,15 @@ class ExistingUserControllerActiveDirectoryUserAllowlistTest
 
 // Tests that Active Directory online login succeeds on the Active Directory
 // managed device.
-// TODO(crbug.com/1148771): Test is flaky.
 IN_PROC_BROWSER_TEST_F(ExistingUserControllerActiveDirectoryTest,
-                       DISABLED_ActiveDirectoryOnlineLogin_Success) {
+                       ActiveDirectoryOnlineLogin_Success) {
   LoginAdOnline();
 }
 
 // Tests if DisabledAuthNegotiateCnameLookup changes trigger updating user
 // Kerberos files.
-// TODO(crbug.com/1148771): Test is flaky.
 IN_PROC_BROWSER_TEST_F(ExistingUserControllerActiveDirectoryTest,
-                       DISABLED_PolicyChangeTriggersFileUpdate) {
+                       PolicyChangeTriggersFileUpdate) {
   LoginAdOnline();
 
   ApplyPolicyAndWaitFilesChanged(false /* enable_dns_cname_lookup */);
@@ -1008,10 +1006,8 @@ IN_PROC_BROWSER_TEST_F(ExistingUserControllerActiveDirectoryTest,
 
 // Tests if user Kerberos files changed D-Bus signal triggers updating user
 // Kerberos files.
-// TODO(crbug.com/1148771): Test is flaky.
-IN_PROC_BROWSER_TEST_F(
-    ExistingUserControllerActiveDirectoryTest,
-    DISABLED_UserKerberosFilesChangedSignalTriggersFileUpdate) {
+IN_PROC_BROWSER_TEST_F(ExistingUserControllerActiveDirectoryTest,
+                       UserKerberosFilesChangedSignalTriggersFileUpdate) {
   LoginAdOnline();
 
   // Set authpolicyd's copy of the Kerberos files and wait until Chrome's copy
@@ -1026,9 +1022,8 @@ IN_PROC_BROWSER_TEST_F(
 
 // Tests that Active Directory offline login succeeds on the Active Directory
 // managed device.
-// TODO(crbug.com/1148771): Test is flaky.
 IN_PROC_BROWSER_TEST_F(ExistingUserControllerActiveDirectoryTest,
-                       DISABLED_ActiveDirectoryOfflineLogin_Success) {
+                       ActiveDirectoryOfflineLogin_Success) {
   ExpectLoginSuccess();
   UserContext user_context(user_manager::UserType::USER_TYPE_ACTIVE_DIRECTORY,
                            ad_account_id_);