Update code example in File Upload topic (#18424)

Author: guardrex

aspnetcore/mvc/models/file-uploads.md

@@ -640,14 +640,14 @@ For apps hosted by Kestrel, the default maximum request body size is 30,000,000
 ```csharp
 public static IHostBuilder CreateHostBuilder(string[] args) =>
     Host.CreateDefaultBuilder(args)
-        .ConfigureKestrel((context, options) =>
-        {
-            // Handle requests up to 50 MB
-            options.Limits.MaxRequestBodySize = 52428800;
-        })
         .ConfigureWebHostDefaults(webBuilder =>
         {
-            webBuilder.UseStartup<Startup>();
+            webBuilder.ConfigureKestrel((context, options) =>
+            {
+                // Handle requests up to 50 MB
+                options.Limits.MaxRequestBodySize = 52428800;
+            })
+            .UseStartup<Startup>();
         });
 ```