added sleep to give time for event to be received

Signed-off-by: Florian Bacher <[email protected]>

test/OpenFeature.Tests/OpenFeatureEventTests.cs

@@ -55,6 +55,7 @@ public async Task API_Level_Event_Handlers_Should_Be_Registered()
             var testProvider = new TestProvider();
             await Api.Instance.SetProvider(testProvider);
 
+            Thread.Sleep(1000);
             eventHandler.Received().Invoke(Arg.Is<ProviderEventPayload>(payload => payload.ProviderName == testProvider.GetMetadata().Name));
         }