Hide/remove some JSON utility classes (#1039)

dotnet/samples/AgentWebChat/AgentWebChat.Web/AgentDiscoveryClient.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System.Text.Json;
-using Microsoft.Agents.AI.Hosting;
 
 namespace AgentWebChat.Web;
 
@@ -13,7 +12,7 @@ public class AgentDiscoveryClient(HttpClient httpClient, ILogger<AgentDiscoveryC
         response.EnsureSuccessStatusCode();
 
         var json = await response.Content.ReadAsStringAsync(cancellationToken);
-        var agents = JsonSerializer.Deserialize<List<AgentDiscoveryCard>>(json, AgentHostingJsonUtilities.DefaultOptions) ?? [];
+        var agents = JsonSerializer.Deserialize<List<AgentDiscoveryCard>>(json) ?? [];
 
         logger.LogInformation("Retrieved {AgentCount} agents from the API", agents.Count);
         return agents;