Add back InternalTesting using

Author: halter73

src/Components/test/E2ETest/Tests/RoutingTest.cs

@@ -9,6 +9,7 @@
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;
 using Microsoft.AspNetCore.E2ETesting;
+using Microsoft.AspNetCore.InternalTesting;
 using OpenQA.Selenium;
 using OpenQA.Selenium.Interactions;
 using Xunit.Abstractions;