Remove unused version entries

Author: stephentoub

Directory.Packages.props

@@ -25,8 +25,6 @@
     <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="8.0.0" />
     <PackageVersion Include="System.IO.Pipelines" Version="8.0.0" />
     <PackageVersion Include="System.Net.ServerSentEvents" Version="$(System10Version)" />
-    <PackageVersion Include="System.Text.Json" Version="8.0.5" />
-    <PackageVersion Include="System.Threading.Channels" Version="8.0.0" />
   </ItemGroup>
 
   <!-- Product dependencies .NET 9 -->