Clean up how IHttpContextAccessor is added

src/Microsoft.AspNetCore.SpaServices/Prerendering/PrerenderingServiceCollectionExtensions.cs

@@ -1,10 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.NodeServices;
-using Microsoft.AspNetCore.SpaServices.Prerendering;
-using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.AspNetCore.SpaServices.Prerendering;
 
 namespace Microsoft.Extensions.DependencyInjection
 {
@@ -20,7 +14,7 @@ namespace Microsoft.Extensions.DependencyInjection
         /// <param name="serviceCollection">The <see cref="IServiceCollection"/>.</param>
         public static void AddSpaPrerenderer(this IServiceCollection serviceCollection)
         {
-            serviceCollection.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
+            serviceCollection.AddHttpContextAccessor();
             serviceCollection.AddSingleton<ISpaPrerenderer, DefaultSpaPrerenderer>();
         }
     }