[Bug] Investigate `ExecuteWorkflowAsync_PollingBehavior_Autoscaling` flake

[cretz]

Describe the bug

In rare situations, Temporalio.Tests.Worker.WorkflowWorkerTests.ExecuteWorkflowAsync_PollingBehavior_Autoscaling fails with:

  Failed Temporalio.Tests.Worker.WorkflowWorkerTests.ExecuteWorkflowAsync_PollingBehavior_Autoscaling [113 ms]
  Error Message:
   The collection was expected to contain a single element, but it was empty.
  Stack Trace:
     at Temporalio.Tests.Worker.WorkflowWorkerTests.<>c__DisplayClass222_0.<<ExecuteWorkflowAsync_PollingBehavior_Autoscaling>b__0>d.MoveNext() in /home/runner/work/sdk-dotnet/sdk-dotnet/tests/Temporalio.Tests/Worker/WorkflowWorkerTests.cs:line 7561
--- End of stack trace from previous location ---
   at Temporalio.Tests.Worker.WorkflowWorkerTests.<>c__DisplayClass229_0`1.<<ExecuteWorkerAsync>b__0>d.MoveNext() in /home/runner/work/sdk-dotnet/sdk-dotnet/tests/Temporalio.Tests/Worker/WorkflowWorkerTests.cs:line 7732
--- End of stack trace from previous location ---
   at Temporalio.Worker.TemporalWorker.<>c__DisplayClass29_0`1.<<ExecuteAsync>b__0>d.MoveNext() in /home/runner/work/sdk-dotnet/sdk-dotnet/src/Temporalio/Worker/TemporalWorker.cs:line 271
--- End of stack trace from previous location ---
   at Temporalio.Worker.TemporalWorker.ExecuteInternalAsync(Func`1 untilComplete, CancellationToken stoppingToken) in /home/runner/work/sdk-dotnet/sdk-dotnet/src/Temporalio/Worker/TemporalWorker.cs:line 430
   at Temporalio.Worker.TemporalWorker.ExecuteInternalAsync(Func`1 untilComplete, CancellationToken stoppingToken) in /home/runner/work/sdk-dotnet/sdk-dotnet/src/Temporalio/Worker/TemporalWorker.cs:line 445
   at Temporalio.Worker.TemporalWorker.ExecuteAsync[TResult](Func`1 untilComplete, CancellationToken stoppingToken) in /home/runner/work/sdk-dotnet/sdk-dotnet/src/Temporalio/Worker/TemporalWorker.cs:line 270
   at Temporalio.Tests.Worker.WorkflowWorkerTests.ExecuteWorkerAsync[TWorkflow,TResult](Func`2 action, TemporalWorkerOptions options, IWorkerClient client) in /home/runner/work/sdk-dotnet/sdk-dotnet/tests/Temporalio.Tests/Worker/WorkflowWorkerTests.cs:line 7745
   at Temporalio.Tests.Worker.WorkflowWorkerTests.ExecuteWorkflowAsync_PollingBehavior_Autoscaling() in /home/runner/work/sdk-dotnet/sdk-dotnet/tests/Temporalio.Tests/Worker/WorkflowWorkerTests.cs:line 7551
--- End of stack trace from previous location ---