fix: update provider status to Fatal during disposal (#580)

Signed-off-by: André Silva <[email protected]>

Author: askpt

src/OpenFeature.Providers.MultiProvider/MultiProvider.cs

@@ -280,6 +280,7 @@ public async ValueTask DisposeAsync()
         {
             this._initializationSemaphore.Dispose();
             this._shutdownSemaphore.Dispose();
+            this._providerStatus = ProviderStatus.Fatal;
         }
     }