Fix EventSourced Stash filtering out identical envelopes (#7375)

Author: Arkatufus

src/core/Akka/Actor/Stash/Internal/AbstractStash.cs

@@ -180,7 +180,7 @@ public void Prepend(IEnumerable<Envelope> envelopes)
         {
             // since we want to save the order of messages, but still prepending using AddFirst,
             // we must enumerate envelopes in reversed order
-            foreach (var envelope in envelopes.Distinct().Reverse())
+            foreach (var envelope in envelopes.Reverse())
             {
                 _theStash.AddFirst(envelope);
             }