Mark 405 response code as "success" for AI (#6669)

Author: Scott Bommarito

src/NuGetGallery/App_Start/OwinStartup.cs

@@ -92,6 +92,7 @@ public static void Configuration(IAppBuilder app)
 
                     processor.SuccessfulResponseCodes.Add(400);
                     processor.SuccessfulResponseCodes.Add(404);
+                    processor.SuccessfulResponseCodes.Add(405);
 
                     return processor;
                 });