Remove the unused dependency (Azure#50497)

Author: nick863

sdk/ai/Azure.AI.Agents.Persistent/src/Azure.AI.Agents.Persistent.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>This is the Azure.AI.Agents.Persistent client library for developing .NET applications with rich experience.</Description>
     <AssemblyTitle>Microsoft Azure.AI.Agents.Persistent client library</AssemblyTitle>
@@ -16,8 +16,6 @@
 
   <ItemGroup>
     <PackageReference Include="Azure.Core" />
-    <PackageReference Include="Azure.Identity" />
-    <PackageReference Include="System.ClientModel" />
   </ItemGroup>
 
   <!-- Shared source from Azure.Core -->