Bump Microsoft.NETFramework.ReferenceAssemblies and System.Collection…

…s.Immutable

Bumps [Microsoft.NETFramework.ReferenceAssemblies](https://github.com/Microsoft/dotnet) and [System.Collections.Immutable](https://github.com/dotnet/runtime). These dependencies needed to be updated together.

Updates `Microsoft.NETFramework.ReferenceAssemblies` from 1.0.3 to 1.0.3
- [Commits](https://github.com/Microsoft/dotnet/commits)

Updates `System.Collections.Immutable` from 8.0.0 to 9.0.2
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.0...v9.0.2)

---
updated-dependencies:
- dependency-name: Microsoft.NETFramework.ReferenceAssemblies
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: System.Collections.Immutable
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

src/TestFixture/TestFixture.csproj

@@ -15,7 +15,7 @@
   </PropertyGroup>  
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
-    <PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
+    <PackageReference Include="System.Collections.Immutable" Version="9.0.2" />
     <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" />
   </ItemGroup>