Write objects in reverse order instead of root object twice (#470)

src/Speckle.Sdk/Pipelines/Send/SendPipeline.cs

@@ -36,28 +36,22 @@ public sealed class SendPipeline : IDisposable
     _diskStore = diskStore;
   }
 
-  private UploadItem _lastItem;
-
   public async Task<ObjectReference> Process(Base @base)
   {
     var results = _serializer.Serialize(@base).ToArray();
     var first = results.First();
-    foreach (var item in results)
+    // .Reverse ensures the root commit object is written last.
+    foreach (var item in results.Reverse())
     {
       // we're not doing fire and forget here so that we get the backpressure from the uploader
       await _diskStore.PushAsync(item).ConfigureAwait(false);
     }
 
-    // NOTE: this is important to keep track of. When we serialze an object, we get back a list of objects, with the first one being the original root.
-    // In the case of the commit root object, this means the last object is not necessarily the root; we therefore need to manually track its existance here
-    // and ensure it's the last one through in the uploader's stream. See WaitForUpload down below.
-    _lastItem = first;
     return first.Reference;
   }
 
   public async Task WaitForUpload()
   {
-    await _diskStore.PushAsync(_lastItem).ConfigureAwait(false);
     using DisposableFile tempFile = await _diskStore.CompleteAsync().ConfigureAwait(false);
 
     using Stream fileStreamUpload = new FileStream(