Update _Imports.razor to include sections namespace (#49166)

Author: danroth27

src/Components/WebView/Samples/PhotinoPlatform/testassets/PhotinoTestApp/_Imports.razor

@@ -2,6 +2,7 @@
 @using System.Net.Http.Json
 @using Microsoft.AspNetCore.Components.Forms
 @using Microsoft.AspNetCore.Components.Routing
+@using Microsoft.AspNetCore.Components.Sections
 @using Microsoft.AspNetCore.Components.Web
 @using Microsoft.AspNetCore.Components.Web.Virtualization
 @using Microsoft.JSInterop