Account Manager flag cleanup: AD credentials manager

Chrome OS Account Manager has been turned on by default on ToT, and has
been launched via Finch for some time now. Clean up its flag's usages in
Active Directory credentials manager.

TBR=rsorokin@chromium.org

Bug: 1009960
Change-Id: Id81addd05162e2bd911b555ab47f24248a9312e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832212Reviewed-by: Kush Sinha <sinhak@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702061}

chrome/browser/chromeos/authpolicy/auth_policy_credentials_manager.cc

@@ -26,7 +26,6 @@
 #include "chrome/grit/theme_resources.h"
 #include "chromeos/components/account_manager/account_manager.h"
 #include "chromeos/components/account_manager/account_manager_factory.h"
-#include "chromeos/constants/chromeos_features.h"
 #include "chromeos/dbus/auth_policy/auth_policy_client.h"
 #include "chromeos/network/network_handler.h"
 #include "chromeos/network/network_state.h"
@@ -50,9 +49,6 @@ constexpr char kProfileSigninNotificationId[] = "chrome://settings/signin/";
 // |profile| is a non-owning pointer to |Profile|.
 // |account_id| is the |AccountId| for the Device Account.
 void SetupAccountManager(Profile* profile, const AccountId& account_id) {
-  if (!features::IsAccountManagerEnabled())
-    return;
-
   AccountManagerFactory* factory =
       g_browser_process->platform_part()->GetAccountManagerFactory();
   DCHECK(factory);