Increase Hosting test delay to fix flaky BackgroundServiceAsyncExcept…

…ionGetsLogged test.

Fix dotnet#43389

src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs

@@ -1372,7 +1372,9 @@ private class AsyncThrowingService : BackgroundService
         {
             protected override async Task ExecuteAsync(CancellationToken stoppingToken)
             {
-                await Task.Yield();
+                // Delay long enough that BackgroundService.StartAsync gets a chance to complete
+                // before the exception is thrown. But don't delay for too long so the test completes quickly.
+                await Task.Delay(50);
 
                 throw new Exception("Background Exception");
             }