remove Distinct() in inventory tracking

These cover very rare edge cases with invalid inventory data, so it's not really worth the added performance hit of handling them. The next commits will avoid the error if duplicates do occur.

src/SMAPI/Framework/StateTracking/ChestTracker.cs

@@ -48,7 +48,6 @@ internal class ChestTracker : IDisposable
 
         this.StackSizes = this.Chest.Items
             .Where(n => n != null)
-            .Distinct()
             .ToDictionary(n => n, n => n.Stack);
     }
 

src/SMAPI/Framework/StateTracking/PlayerTracker.cs

@@ -137,7 +137,6 @@ internal class PlayerTracker : IDisposable
     {
         return this.Player.Items
             .Where(n => n != null)
-            .Distinct()
             .ToDictionary(n => n, n => n.Stack);
     }
 }