Remove header instead

Fixes #4837

Author: johnsimons

src/ServiceControl/Recoverability/Editing/EditHandler.cs

@@ -67,7 +67,7 @@ public async Task Handle(EditAndSend message, IMessageHandlerContext context)
             var outgoingMessage = BuildMessage(message);
             // mark the new message with a link to the original message id
             outgoingMessage.Headers.Add("ServiceControl.EditOf", message.FailedMessageId);
-            outgoingMessage.Headers["ServiceControl.Retry.AcknowledgementQueue"] = "";
+            outgoingMessage.Headers.Remove("ServiceControl.Retry.AcknowledgementQueue");
             var address = ApplyRedirect(attempt.FailureDetails.AddressOfFailingEndpoint, redirects);
 
             if (outgoingMessage.Headers.TryGetValue("ServiceControl.RetryTo", out var retryTo))