Fix typo in class name of examples. (#18936)

Author: nikonthethird

aspnetcore/blazor/fundamentals/additional-scenarios.md

@@ -24,7 +24,7 @@ To configure SignalR's underlying client to send credentials, such as cookies or
 * Use <xref:Microsoft.AspNetCore.Components.WebAssembly.Http.WebAssemblyHttpRequestMessageExtensions.SetBrowserRequestCredentials%2A> to set <xref:Microsoft.AspNetCore.Components.WebAssembly.Http.BrowserRequestCredentials.Include> on cross-origin [`fetch`](https://developer.mozilla.org/docs/Web/API/Fetch_API/Using_Fetch) requests:
 
   ```csharp
-  public class IncludeRequestCredentialsMessagHandler : DelegatingHandler
+  public class IncludeRequestCredentialsMessageHandler : DelegatingHandler
   {
       protected override Task<HttpResponseMessage> SendAsync(
           HttpRequestMessage request, CancellationToken cancellationToken)
@@ -42,7 +42,7 @@ To configure SignalR's underlying client to send credentials, such as cookies or
       .WithUrl(new Uri("http://signalr.example.com"), options =>
       {
           options.HttpMessageHandlerFactory = innerHandler => 
-              new IncludeRequestCredentialsMessagHandler { InnerHandler = innerHandler };
+              new IncludeRequestCredentialsMessageHandler { InnerHandler = innerHandler };
       }).Build();
   ```