Use correct tracking object on Line

Author: MatthewSteeples

Xero.Api/Core/Model/Line.cs

@@ -42,11 +42,11 @@ public class Line : CoreData, IHasId
         //There is an inconsistency with TrackingCatgories on JournalLines between Journals and ManualJournals.
         //Use TrackingCategories with Journals
         [DataMember(EmitDefaultValue = false)]
-        public List<TrackingCategory> TrackingCategories { get; set; }
+        public ItemTracking TrackingCategories { get; set; }
 
         //Use Tracking with ManualJournals
         [DataMember(EmitDefaultValue = false)]
-        public List<TrackingCategory> Tracking { get; set; }
+        public ItemTracking Tracking { get; set; }
 
         [DataMember(Name = "LineAmount", EmitDefaultValue = false)]
         public decimal Amount { get; set; }