.Net: Fix use of InternalsVisibleTo (#3398)

### Motivation and Context

Fix release build failure

### Contribution Checklist

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

dotnet/src/Experimental/Orchestration.Flow/Experimental.Orchestration.Flow.csproj

@@ -20,9 +20,7 @@
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
-    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
-      <_Parameter1>SemanticKernel.Experimental.Orchestration.Flow.UnitTests</_Parameter1>
-    </AssemblyAttribute>
+    <InternalsVisibleTo Include="SemanticKernel.Experimental.Orchestration.Flow.UnitTests" />
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="YamlDotNet" />