CookieSyncManager deprecated after API 21

[LiliWeiSE]

Hi,

I found that CookieSyncManager.getInstance is invoked in DDGApplication. This class is deprecated since API 21. (doc) I understand it is used to avoid crash bugs for CookieManager, but after API 21, CookieManager can work well alone.

I also found a related Google issue discussion: https://issuetracker.google.com/issues/37014570. They fixed the document and indicated that CookieSyncManager is no longer needed after API 21.