message: fixed errant itemgroup element in C# test project
  errant save
diff: <Compile Include="..\nested_namespace_test\nested_namespace_test3_generated.cs">
  <Link>nested_namespace_test\nested_namespace_test3_generated.cs</Link>
  </Compile>
  - </ItemGroup>
  <Compile Include="Assert.cs" />
  <Compile Include="ByteBufferTests.cs" />
  <Compile Include="FlatBufferBuilderTests.cs" />
  