update focus_mangaer

com.unity.uiwidgets/Runtime/widgets/focus_manager.cs

 
         public FocusAttachment _attachment;
 
-<<<<<<< HEAD
+
-=======
-        IEnumerable<FocusNode> descendants {
->>>>>>> parent of a10f14fb... Merge branch 'dev_1.17.5' into shiyun/skia
             get {
                 if (_descendants == null) {
                     List<FocusNode> result = new List<FocusNode>();