Remove outdated comment in System.CM.Composition.Tests (dotnet#39839)

We don't plan to add a .NETFramework test configuration for this library anymore.

src/libraries/System.ComponentModel.Composition/tests/System.ComponentModel.Composition.Tests.csproj

@@ -1,5 +1,4 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <!-- TODO: Add net472 configuration after OOB package bug is fixed: https://github.com/dotnet/runtime/issues/23497 -->
   <PropertyGroup>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
@@ -173,4 +172,4 @@
     <!-- Some internal types are needed, so we reference the implementation assembly, rather than the reference assembly. -->
     <ProjectReference Include="..\src\System.ComponentModel.Composition.csproj" SkipUseReferenceAssembly="true" />
   </ItemGroup>
-</Project>
+</Project>