Remove IsElementStale method and use existing WebDriverExtensions.IsStale (#64550)

* Initial plan

* Remove IsElementStale and use WebDriverExtensions.IsStale

Co-authored-by: ilonatommy <[email protected]>

* Remove unused private IsElementStale method from EnhancedNavigationTest.cs

Co-authored-by: ilonatommy <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: ilonatommy <[email protected]>

Author: Copilot

src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Components.TestServer.RazorComponents;
+using Microsoft.AspNetCore.Components.E2ETest;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;
 using Microsoft.AspNetCore.Components.E2ETests.ServerExecutionTests;