Revert "[Settings] Support getSystemService(Class<T>)"

This reverts commit d5ccde31a8.

Reason for revert: failure on test cases

Change-Id: I0a179a6ebb5ef1dec566ce6e8facd5f3b82d7c8a

src/com/android/settings/deviceinfo/firmwareversion/FirmwareVersionDetailPreferenceController.java

@@ -49,7 +49,7 @@ public class FirmwareVersionDetailPreferenceController extends BasePreferenceCon
 
     public FirmwareVersionDetailPreferenceController(Context context, String key) {
         super(context, key);
-        mUserManager = mContext.getSystemService(UserManager.class);
+        mUserManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);
         initializeAdminPermissions();
     }