Account Manager cleanup: remove enabling AM in tests

Account Manager is enabled by default now. Merge
ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled
to ChromeOsMirrorAccountConsistency tests.

Bug: 1007927
Change-Id: Ic3362561c8a9cc0696b8420994ba087b44015f79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824102
Commit-Queue: Anastasiia Nikolaienko <anastasiian@chromium.org>
Reviewed-by: Kush Sinha <sinhak@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700655}

chrome/browser/signin/chromeos_mirror_account_consistency_browsertest.cc

@@ -143,37 +143,15 @@ IN_PROC_BROWSER_TEST_F(ChromeOsMirrorAccountConsistencyTest,
                               "consistency_enabled_by_default=false");
 }
 
-class ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled
-    : public ChromeOsMirrorAccountConsistencyTest {
- public:
-  ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled() = default;
-  ~ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled() override =
-      default;
-
-  void SetUp() override {
-    scoped_feature_list_.InitAndEnableFeature(
-        chromeos::features::kAccountManager);
-    ChromeOsMirrorAccountConsistencyTest::SetUp();
-  }
-
- private:
-  base::test::ScopedFeatureList scoped_feature_list_;
-
-  DISALLOW_COPY_AND_ASSIGN(
-      ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled);
-};
-
-IN_PROC_BROWSER_TEST_F(
-    ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled,
-    PRE_TestMirrorRequestChromeOsNotChildAccount) {
+IN_PROC_BROWSER_TEST_F(ChromeOsMirrorAccountConsistencyTest,
+                       PRE_TestMirrorRequestChromeOsNotChildAccount) {
   RegisterUser(account_id_);
   chromeos::StartupUtils::MarkOobeCompleted();
 }
 
-// Mirror is not enabled for non-child accounts.
-IN_PROC_BROWSER_TEST_F(
-    ChromeOsMirrorAccountConsistencyTestWithAccountManagerEnabled,
-    TestMirrorRequestChromeOsNotChildAccount) {
+// Mirror is enabled for non-child accounts.
+IN_PROC_BROWSER_TEST_F(ChromeOsMirrorAccountConsistencyTest,
+                       TestMirrorRequestChromeOsNotChildAccount) {
   // Not a child user.
   LoginUser(account_id_);