Update AsyncQueue.cs (#54)

#53 fixed memory leak in AsyncQueue

Co-authored-by: Pavel Krupets <pkrupets@mparticle.com>
diff --git a/src/DotPulsar/Internal/AsyncQueue.cs b/src/DotPulsar/Internal/AsyncQueue.cs
index 355bd32..6225138 100644
--- a/src/DotPulsar/Internal/AsyncQueue.cs
+++ b/src/DotPulsar/Internal/AsyncQueue.cs
@@ -46,6 +46,7 @@
                     var tcs = _pendingDequeues.First;
                     _pendingDequeues.RemoveFirst();
                     tcs.Value.SetResult(item);
+                    tcs.Value.Dispose();
                 }
                 else
                     _queue.Enqueue(item);